Review ArticlePhysics of Gamma-Ray Bursts Prompt Emission

Asaf Persquoer

Physics Department University College Cork Cork Ireland

Correspondence should be addressed to Asaf Persquoer apeeruccie

Received 5 December 2014 Accepted 30 March 2015

Academic Editor Dean Hines

Copyright copy 2015 Asaf Persquoer This is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In recent years our understanding of gamma-ray bursts (GRB) prompt emission has been revolutionized due to a combinationof new instruments new analysis methods and novel ideas In this review I describe the most recent observational results andcurrent theoretical interpretation Observationally a major development is the rise of time resolved spectral analysis These ledto (I) identification of a distinguished high energy component with GeV photons often seen at a delay and (II) firm evidence forthe existence of a photospheric (thermal) component in a large number of bursts These results triggered many theoretical effortsaimed at understanding the physical conditions in the inner jet regions I highlight some areas of active theoretical research Theseinclude (I) understanding the role played bymagnetic fields in shaping the dynamics ofGRBoutflow and spectra (II) understandingthe microphysics of kinetic and magnetic energy transfer namely accelerating particle to high energies in both shock waves andmagnetic reconnection layers (III) understanding how subphotospheric energy dissipation broadens the ldquoPlanckrdquo spectrum and(IV) geometrical light aberration effects I highlight some of these efforts and point towards gaps that still exist in our knowledgeas well as promising directions for the future

1 Introduction

In spite of an extensive study for nearly a generationunderstanding of gamma-ray bursts (GRB) prompt emissionstill remains an open questionThemain reason for this is thenature of the prompt emission phase the prompt emissionlasts typically a few seconds (or less) without repetition andwith variable light curve Furthermore the spectra vary fromburst to burst and do not show any clear feature that couldeasily be associated with any simple emission model This isin contrast to the afterglow phase which lasts much longerup to years with (relatively) smooth well characteristicbehavior These features enable afterglow studies using longterm multiwaveband observations as well as relatively easycomparison with theories

Nonetheless I think it is fair to claim that in recentyears understanding of GRB prompt emission has beenrevolutionized This follows the launch of Swift satellite in2004 and Fermi satellite in 2008These satellites enable muchmore detailed studies of the prompt emission both in thespectral and temporal domains The new data led to therealization that the observed spectra are composed of severaldistinctive components (I) A thermal component identified

on top of a nonthermal spectra was observed in a largenumber of bursts This component shows a unique temporalbehavior (II) There is evidence that the very high energy(gt GeV) part of the spectra evolves differently than the lowerenergy part and hence is likely to have a separate origin (III)The sharp cutoff in the light curves of many GRBs observedby Swift enables a clear discrimination between the promptand the afterglow phases

The decomposition of the spectra into separate compo-nents presumably with different physical origin enabled anindependent study of the properties of each component aswell as study of the complex connection between the differentcomponents Thanks to these studies we are finally reachinga critical point in which a self-consistent physical pictureof the GRB prompt emission more complete than ever isemergingThis physical insight is of course a crucial link thatconnects the physics ofGRBprogenitor starswith that of theirenvironments

Many of the ideas gained in these studies are relevantto many other astronomical objects such as active galacticnuclei (AGNs) X-ray binaries (XRBs) and tidal disruptionevents (TDEs) All these transient objects share the common

Hindawi Publishing CorporationAdvances in AstronomyVolume 2015 Article ID 907321 37 pageshttpdxdoiorg1011552015907321

2 Advances in Astronomy

feature of having (trans)relativistic jetted outflowsThereforedespite the obvious differences many similarities betweenvarious underlying physical processes in these objects and inGRBs are likely to exist These include the basic questions ofjet launching and propagation as well as the microphysicsof energy transfer via magnetic reconnection and particleacceleration to high energies Furthermore understandingthe physical conditions that exist during the prompt emissionphase enables the study of other fundamental questions suchas whether GRBs are sources of (ultra-high energy) cosmicrays and neutrinos as well as the potential of detectinggravitational waves associated with GRBs

In this review I will describe the current (December2014) observational status as well as the emerging theoreticalpicture I will emphasise a major development of recentyears namely the realization that photospheric emissionmayplay a key role both directly and indirectly as part of theobserved spectra I should stress though that in spite ofseveral major observational and theoretical breakthroughsthat took place in recent years our understanding is still farfrom being complete I will discuss the gaps that still exist inour knowledge and novel ideas raised in addressing them Iwill point to current scientific efforts which are focused ondifferent sometimes even perpendicular directions

The rapid progress in this field is the cause of the factthat in the past decade there have been very many excellentreviews covering various aspects of GRB phenomenologyand physics A partial list includes reviews by Waxman [1]Piran [2] Zhang and Meszaros [3] Meszaros [4] Nakar [5]Zhang [6] Fan and Piran [7] Gehrels et al [8] Atteia andBoer [9] Gehrels andMeszaros [10] Bucciantini [11] Gehrelsand Razzaque [12] Daigne [13] Zhang [14] Kumar andZhang [15] Berger [16] and Meszaros and Rees [17] My goalhere is not to compete with these reviews but to highlightsome of the recent partially still controversial results anddevelopments in this field as well as pointing into current andfuture directions which are promising paths

This review is organized as follows In Section 2 I dis-cuss the current observational status I discuss the lightcurves (Section 21) observed spectra (Section 22) polar-ization (Section 23) counterparts at high and low energies(Section 24) and notable correlations (Section 25) I partic-ularly emphasise the different models used today in fittingthe prompt emission spectra Section 3 is devoted to theo-retical ideas To my opinion the easiest way to understandthe nature of GRBs is to follow the various episodes ofenergy transfer that occur during the GRB evolution I thusbegin by discussing models of GRB progenitors (Section 31)that provide the source of energy This follows by dis-cussing models of relativistic expansion both ldquohotrdquo (photon-dominated) (Section 32) and ldquocoldrdquo (magnetic-dominated)(Section 33) I then discuss recent progress in understandinghow dissipation of the kinetic andor magnetic energy isused in accelerating particles to high-energies (Section 34)I complete with the discussion of the final stage of energyconversion namely radiative processes by the hot particlesas well as the photospheric contribution (Section 35) whichlead to the observed signal I conclude with a look into thefuture in Section 4

2 Key Observational Properties

21 Light Curves Themost notable property of GRB promptemission light curve is that it is irregular diverse andcomplex No two gamma-ray bursts light curves are identicala fact which obviously makes their study challenging Whilesome GRBs are extremely variable with variability timescale in the millisecond range others are much smootherSome have only a single peak while others show multi-ple peaks see Figure 1 Typically individual peaks are notsymmetric but show a ldquofast rise exponential decayrdquo (FRED)behavior

The total duration of GRB prompt emission is tradi-tionally defined by the ldquo11987990rdquo parameter which is the timeinterval in the epoch when 5 and 95 of the total fluenceare detected As thoroughly discussed by Kumar and Zhang[15] this (arbitrary) definition is very subjective due to manyreasons (1) It depends on the energy range and sensitivityof the different detectors (2) Different intrinsic light curvessome light curves are very spiky with gaps between the spikeswhile others are smooth (3) no discrimination is madebetween the ldquopromptrdquo phase and the early afterglow emission(4) it does not take into account the difference in redshiftsbetween the bursts which can be substantial

In spite of these drawbacks11987990 is still themost commonlyused parameter in describing the total duration of the promptphase While 11987990 is observed to vary between millisecondsand thousands of seconds (the longest to date is GRB111209Awith duration of sim25 times 104 s [18]) from the early 1990s itwas noted that the 11987990 distribution of GRBs is bimodal [19]About ≲14 of GRBs in the BATSE catalog are ldquoshortrdquo withaverage 11987990 of sim02ndash03 s and roughly 34 are ldquolongrdquo withaverage 11987990 asymp 20ndash30 s [20] The boundary between thesetwo distributions is at sim2 s Similar results are obtained byFermi (see Figure 2) though the subjective definition of 11987990results in a bit different ratio where only 17 of Fermi-GBMbursts are considered as ldquoshortrdquo the rest being long [21ndash23]Similar conclusion though with much smaller sample andeven lesser fraction of short GRBs are observed in the Swift-Bat catalog [24] and by Integral [25] These results do notchange if instead one uses 11987950 parameter defined in a similarway

These results are accompanied by different hardness ratio(the ratio between the observed photon flux at the highand low energy bands of the detector) where short burstsare on average harder (higher ratio of energetic photons)than long ones [19] Other clues for different origin arethe association of only the long GRBs with core collapsesupernova of type Ibc [26ndash32] which are not found in shortGRBs [33] association of short GRBs to galaxies with littlestar-formation (as opposed to long GRBs which are foundin star forming galaxies) and residing at different locationswithin their host galaxies than longGRBs [34ndash41] Altogetherthese results thus suggest two different progenitor classesHowever a more careful analysis reveals a more complexpicture with many outliers to these rules (eg [42ndash49]) Itis therefore possible maybe even likely that the populationof short GRBs may have more than a single progenitor

Advances in Astronomy 3

150

100

50

0minus5 60 minus5 40

Time (s)50

Time (s) Time (s)

minus5 20Time (s)

minus20 80 minus2 8

minus5 20

Time (s)

minus2 40 minus2 50

minus2 50

minus5 100

50 300Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

20

15

10

5

0

20

15

10

5

0

30

25

20

15

10

5

0

18

16

14

12

10

8

6

12

10

8

6

4

2

2

400

300

200

100

0

9

8

7

6

5

4

3

6

5

4

3

100

80

60

40

20

0

12

10

8

6

4

2

150

100

50

0

GRB 910503Trig 143

GRB 910711Trig 512

GRB 920216BTrig 1406

GRB 920221Trig 1425

GRB 921003ATrig 1974

GRB 921022BTrig 1997

GRB 921123ATrig 2067

GRB 930131ATrig 2151

GRB 931008CTrig 2571

GRB 940210Trig 2812

GRB 990316ATrig 7475

GRB 991216Trig 7906

Figure 1 Light curves of 12 bright gamma-ray bursts detected by BATSE Gamma-ray bursts light curves display a tremendous amount ofdiversity and few discernible patterns This sample includes short events and long events (duration ranging from milliseconds to minutes)events with smooth behavior and single peaks and events with highly variable erratic behavior with many peaks Created by Daniel Perleywith data from the public BATSE archive (httpgammaraymsfcnasagovbatsegrbcatalog)

(or physical origin) In addition there have been severalclaims for a small third class of ldquointermediaterdquo GRBs with11987990 sim 2 s [50ndash53] but this is still controversial (eg [48 54])

To further add to the confusion the light curve itselfvaries with energy band (eg Figure 3) One of Fermirsquos mostimportant results tomy view is the discovery that the highest

energy photons (in the LAT band) are observed to both (I)lag behind the emission at lower energies and (II) last longerBoth these results are seen in Figure 3 Similarly the widthof individual pulses is energy dependent It was found thatthe pulse width 120596 varies with energy 120596(119864) prop 119864

minus120572 with120572 sim 03ndash04 [55 56]

4 Advances in Astronomy

0

50

100

150

Num

ber o

f bur

sts

001 010 100 1000 10000 100000T90 (s)

Figure 2 Distribution of GRB durations (11987990) of 953 bursts in theFermi-GBM (50ndash300 keV energy range) Taken from the 2nd Fermicatalog [23] 159 (17) of the bursts are ldquoshortrdquo

a b c d e

00 3

677

158

547

1008

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)

(Cou

nts

bin)GBM NaI3 + NaI4

(8keVndash260keV)

GBM BGO0(260keVndash5MeV)

LAT(no selection)

LAT(gt100MeV)

LAT(gt1GeV)

minus20 0 20 40 60 80 100Time since trigger (s)

Time since trigger (s)

150010005000

150010005000

4002000

3002001000

3002001000

5

0

3210

3000200010000

1000

500

0

6004002000

151050

6420

0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

151

050

10

5

0

400

200

0(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

Figure 3 Light curves for GRB 080916C observed with the GBMand the LAT detectors on board the Fermi satellite from lowest tohighest energies The top graph shows the sum of the counts in the8 to 260 keV energy band of two NaI detectors The second is thecorresponding plot for BGOdetector 0 between 260 keV and 5MeVThe third shows all LAT events passing the onboard event filter forgamma-rays (Insets) Views of the first 15 s from the trigger timeIn all cases the bin width is 05 s the per-second counting rate isreported on the right for convenience Taken from Abdo et al [57]

Already in the BATSE era several bursts were foundto have ldquoultra-longrdquo duration having 11987990 exceeding sim103 s(eg [58 59]) Recently several additional bursts were foundin this category (eg GRB 091024A GRB 101225A GRB111209A GRB 121027A and GRB 130925A [18 60ndash63])which raise the idea of a new class of GRBs If these burstsindeed represent a separate class they may have a different

progenitor than that of ldquoregularrdquo long GRBs [62 64 65]However recent analysis showed that bursts with duration11987990 sim 103 s need not belong to a special population whilebursts with 11987990 ≳ 104 s may belong to a separate population[66 67] As the statistics is very low my view is that this isstill an open issue

22 Spectral Properties

221 AWord of Caution Since this is a rapidly evolving fieldone has to be extra careful in describing the spectra of GRBprompt emission As I will show below the observed spectrais in fact sensitive to the analysis method chosen Thusbefore describing the spectra one has to describe the analysismethod

Typically the spectral analysis is based on analyzing fluxintegrated over the entire duration of the prompt emissionnamely the spectra is time-integrated Clearly this is a tradeoff as enough photons need to be collected in order to analyzethe spectra For weak bursts this is the only thing one cando However there is a major drawback here use of the timeintegrated spectra implies that important time-dependentsignals could potentially be lost or at least smeared This caneasily lead to the wrong theoretical interpretation

A second point of caution is the analysis method whichis done by a forward folding technique This means thefollowing First a model spectrum is chosen Second thechosen model is convolved with the detector response andcompared to the detected counts spectrumThird the modelparameters are varied in search for the minimal differencebetween model and data The outcome is the best fittedparameters within the framework of the chosen model Thisanalysis method is the only one that can be used due to thenonlinearity of the detectorrsquos response matrix which makesit impossible to invert

However the need to predetermine the fitted modelimplies that the results are biased by the initial hypothesisTwo different models can fit the data equally well This factwhich is often being ignored by theoreticians is importantto realize when the spectral fits are interpreted Key spectralproperties such as the energy of the spectral peak put strongconstraints on possible emission models Below I show a fewexamples of different analysis methods of the same data thatresult in different spectral peak energies slopes and so forthand therefore lead to different theoretical interpretations

222 The ldquoBandrdquo Model In order to avoid biases towards apreferred physical emission model GRB spectra are tradi-tionally fitted with a mathematical function which is knownas the ldquoBandrdquo function (after the late David Band) [68] Thisfunction had become the standard in this field and is oftenreferred to as ldquoBand modelrdquo The photon number spectra inthis model are given by

119873ph (119864)

= 119860

(

119864

100 keV)

120572

exp(minus 119864

1198640) 119864 lt (120572 minus 120573) 1198640

[

(120572 minus 120573) 1198640100 keV

]

120572minus120573

exp (120573 minus 120572) ( 119864

100 keV)

120573

119864 ge (120572 minus 120573) 1198640

(1)

Advances in Astronomy 5

NaI_03NaI_04

BGO_00LAT

Rate

(cou

ntss

minus1

keVminus1 )

420

minus2minus4

101 102 103 104 105 106 107

Energy (keV)

120590

100

10minus2

10minus4

10minus6

10minus8

(a)

103

102

10

ad

c

b

e

Energy (keV)10 102 103 104 105 106 107

F

(keV

cm

2 s)

(b)

Figure 4 Spectra of GRB 080916C at the five time intervals (andashe) defined in Figure 3 are fitted with a ldquoBandrdquo function (a) Count spectrumfor NaI BGO and LAT in time bin b (b) The model spectra in ]119865] units for all five time intervals in which a flat spectrum would indicateequal energy per decade of photon energy and the changing shapes show the evolution of the spectrum over time The ldquobroken power lawrdquofigure adopted from Abdo et al [57]

This model thus has 4 free parameters low energy spectralslope120572 high energy spectral slope120573 break energyasymp 119864

0 and

an overall normalization 119860 It is found that such a simplisticmodel which resembles a ldquobroken power lawrdquo is capableof providing good fits to many different GRB spectra seeFigure 4 for an example Thus this model is by far the mostwidely used in describing GRB spectra

Some variations of this model have been introduced inthe literature Examples are single power law (PL) ldquosmoothbroken power lawrdquo (SBPL) or ldquoComptonizedmodelrdquo (Comp)(see eg [69ndash72]) These are very similar in nature and donot in general provide a better physical insight

On the downside clearly having only 4 free parametersthis model is unable to capture complex spectral behaviorthat is known now to exist such as the different temporalbehavior of the high energy emission discussed above Evenmore importantly as will be discussed below the limitednumber of freemodel parameters in thismodel can easily leadto wrong conclusions Furthermore this model on purposeis mathematical in nature and therefore fitting the data withthis model does not by itself provide any clue about thephysical origin of the emission In order to obtain such aninsight one has to compare the fitted results to the predictionsof different theoretical models

When using the ldquoBandrdquo model to fit a large number ofbursts the distribution of the key model parameters (thelow and high energy slopes 120572 and 120573 and the peak energy119864peak) is shown to be surprisingly narrow (see Figure 5)The spectral properties of the two categories short and longGRBs detected by both BATSE Integral as well as Fermiare very similar with only minor differences [25 69 71ndash76] The low energy spectral slope is roughly in the rangeminus15 lt 120572 lt 0 averaging at ⟨120572⟩ ≃ minus1 The distribution of

the high energy spectral slope peaks at ⟨120573⟩ ≃ minus2 While typ-ically 120573 lt minus13 many bursts show a very steep 120573 consistentwith an exponential cutoff The peak energy averages around⟨119864peak⟩ ≃ 200 keV and it ranges from tens keV up to simMeV(and even higher in a few rare exceptional bursts)

As can be seen in Figures 4 and 5 the ldquoBandrdquo fits to thespectra have three key spectral properties (1) The promptemission extends to very high energies ≳MeVThis energy isabove the threshold for pair production (119898

119890= 0511MeV)

which is the original motivation for relativistic expansionof GRB outflows (see below) (2) The ldquoBandrdquo fits do notresemble a ldquoPlanckrdquo function hence the reason why thermalemission which was initially suggested as the origin of GRBprompt spectra [77 78] was quickly abandoned and notconsidered as a valid radiation process for a long time (3)Thevalues of the free ldquoBandrdquomodel parameters and in particularthe value of the low energy spectral slope 120572 are not easilyfitted with any simply broadband radiative process such assynchrotron or synchrotron self-Compton (SSC) Althoughin some bursts synchrotron emission could be used to fitthe spectra (eg [79ndash82]) this is not the case in the vastmajority of GRBs [83ndash86] This was noted already in 1998with the term ldquosynchrotron line of deathrdquo coined by Preeceet al [84] to emphasise the inability of the synchrotronemission model to provide good fits to the spectra of (most)GRBs

Indeed these three observational properties introduce amajor theoretical challenge as currently no simple physicallymotivatedmodel is able to provide convincing explanation tothe observed spectra However as already discussed abovethe ldquoBandrdquo fits suffer from several inherent major drawbacksand therefore the obtained results must be treated with greatcare

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

2 Advances in Astronomy

feature of having (trans)relativistic jetted outflowsThereforedespite the obvious differences many similarities betweenvarious underlying physical processes in these objects and inGRBs are likely to exist These include the basic questions ofjet launching and propagation as well as the microphysicsof energy transfer via magnetic reconnection and particleacceleration to high energies Furthermore understandingthe physical conditions that exist during the prompt emissionphase enables the study of other fundamental questions suchas whether GRBs are sources of (ultra-high energy) cosmicrays and neutrinos as well as the potential of detectinggravitational waves associated with GRBs

In this review I will describe the current (December2014) observational status as well as the emerging theoreticalpicture I will emphasise a major development of recentyears namely the realization that photospheric emissionmayplay a key role both directly and indirectly as part of theobserved spectra I should stress though that in spite ofseveral major observational and theoretical breakthroughsthat took place in recent years our understanding is still farfrom being complete I will discuss the gaps that still exist inour knowledge and novel ideas raised in addressing them Iwill point to current scientific efforts which are focused ondifferent sometimes even perpendicular directions

The rapid progress in this field is the cause of the factthat in the past decade there have been very many excellentreviews covering various aspects of GRB phenomenologyand physics A partial list includes reviews by Waxman [1]Piran [2] Zhang and Meszaros [3] Meszaros [4] Nakar [5]Zhang [6] Fan and Piran [7] Gehrels et al [8] Atteia andBoer [9] Gehrels andMeszaros [10] Bucciantini [11] Gehrelsand Razzaque [12] Daigne [13] Zhang [14] Kumar andZhang [15] Berger [16] and Meszaros and Rees [17] My goalhere is not to compete with these reviews but to highlightsome of the recent partially still controversial results anddevelopments in this field as well as pointing into current andfuture directions which are promising paths

This review is organized as follows In Section 2 I dis-cuss the current observational status I discuss the lightcurves (Section 21) observed spectra (Section 22) polar-ization (Section 23) counterparts at high and low energies(Section 24) and notable correlations (Section 25) I partic-ularly emphasise the different models used today in fittingthe prompt emission spectra Section 3 is devoted to theo-retical ideas To my opinion the easiest way to understandthe nature of GRBs is to follow the various episodes ofenergy transfer that occur during the GRB evolution I thusbegin by discussing models of GRB progenitors (Section 31)that provide the source of energy This follows by dis-cussing models of relativistic expansion both ldquohotrdquo (photon-dominated) (Section 32) and ldquocoldrdquo (magnetic-dominated)(Section 33) I then discuss recent progress in understandinghow dissipation of the kinetic andor magnetic energy isused in accelerating particles to high-energies (Section 34)I complete with the discussion of the final stage of energyconversion namely radiative processes by the hot particlesas well as the photospheric contribution (Section 35) whichlead to the observed signal I conclude with a look into thefuture in Section 4

2 Key Observational Properties

21 Light Curves Themost notable property of GRB promptemission light curve is that it is irregular diverse andcomplex No two gamma-ray bursts light curves are identicala fact which obviously makes their study challenging Whilesome GRBs are extremely variable with variability timescale in the millisecond range others are much smootherSome have only a single peak while others show multi-ple peaks see Figure 1 Typically individual peaks are notsymmetric but show a ldquofast rise exponential decayrdquo (FRED)behavior

The total duration of GRB prompt emission is tradi-tionally defined by the ldquo11987990rdquo parameter which is the timeinterval in the epoch when 5 and 95 of the total fluenceare detected As thoroughly discussed by Kumar and Zhang[15] this (arbitrary) definition is very subjective due to manyreasons (1) It depends on the energy range and sensitivityof the different detectors (2) Different intrinsic light curvessome light curves are very spiky with gaps between the spikeswhile others are smooth (3) no discrimination is madebetween the ldquopromptrdquo phase and the early afterglow emission(4) it does not take into account the difference in redshiftsbetween the bursts which can be substantial

In spite of these drawbacks11987990 is still themost commonlyused parameter in describing the total duration of the promptphase While 11987990 is observed to vary between millisecondsand thousands of seconds (the longest to date is GRB111209Awith duration of sim25 times 104 s [18]) from the early 1990s itwas noted that the 11987990 distribution of GRBs is bimodal [19]About ≲14 of GRBs in the BATSE catalog are ldquoshortrdquo withaverage 11987990 of sim02ndash03 s and roughly 34 are ldquolongrdquo withaverage 11987990 asymp 20ndash30 s [20] The boundary between thesetwo distributions is at sim2 s Similar results are obtained byFermi (see Figure 2) though the subjective definition of 11987990results in a bit different ratio where only 17 of Fermi-GBMbursts are considered as ldquoshortrdquo the rest being long [21ndash23]Similar conclusion though with much smaller sample andeven lesser fraction of short GRBs are observed in the Swift-Bat catalog [24] and by Integral [25] These results do notchange if instead one uses 11987950 parameter defined in a similarway

These results are accompanied by different hardness ratio(the ratio between the observed photon flux at the highand low energy bands of the detector) where short burstsare on average harder (higher ratio of energetic photons)than long ones [19] Other clues for different origin arethe association of only the long GRBs with core collapsesupernova of type Ibc [26ndash32] which are not found in shortGRBs [33] association of short GRBs to galaxies with littlestar-formation (as opposed to long GRBs which are foundin star forming galaxies) and residing at different locationswithin their host galaxies than longGRBs [34ndash41] Altogetherthese results thus suggest two different progenitor classesHowever a more careful analysis reveals a more complexpicture with many outliers to these rules (eg [42ndash49]) Itis therefore possible maybe even likely that the populationof short GRBs may have more than a single progenitor

Advances in Astronomy 3

150

100

50

0minus5 60 minus5 40

Time (s)50

Time (s) Time (s)

minus5 20Time (s)

minus20 80 minus2 8

minus5 20

Time (s)

minus2 40 minus2 50

minus2 50

minus5 100

50 300Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

20

15

10

5

0

20

15

10

5

0

30

25

20

15

10

5

0

18

16

14

12

10

8

6

12

10

8

6

4

2

2

400

300

200

100

0

9

8

7

6

5

4

3

6

5

4

3

100

80

60

40

20

0

12

10

8

6

4

2

150

100

50

0

GRB 910503Trig 143

GRB 910711Trig 512

GRB 920216BTrig 1406

GRB 920221Trig 1425

GRB 921003ATrig 1974

GRB 921022BTrig 1997

GRB 921123ATrig 2067

GRB 930131ATrig 2151

GRB 931008CTrig 2571

GRB 940210Trig 2812

GRB 990316ATrig 7475

GRB 991216Trig 7906

Figure 1 Light curves of 12 bright gamma-ray bursts detected by BATSE Gamma-ray bursts light curves display a tremendous amount ofdiversity and few discernible patterns This sample includes short events and long events (duration ranging from milliseconds to minutes)events with smooth behavior and single peaks and events with highly variable erratic behavior with many peaks Created by Daniel Perleywith data from the public BATSE archive (httpgammaraymsfcnasagovbatsegrbcatalog)

(or physical origin) In addition there have been severalclaims for a small third class of ldquointermediaterdquo GRBs with11987990 sim 2 s [50ndash53] but this is still controversial (eg [48 54])

To further add to the confusion the light curve itselfvaries with energy band (eg Figure 3) One of Fermirsquos mostimportant results tomy view is the discovery that the highest

energy photons (in the LAT band) are observed to both (I)lag behind the emission at lower energies and (II) last longerBoth these results are seen in Figure 3 Similarly the widthof individual pulses is energy dependent It was found thatthe pulse width 120596 varies with energy 120596(119864) prop 119864

minus120572 with120572 sim 03ndash04 [55 56]

4 Advances in Astronomy

0

50

100

150

Num

ber o

f bur

sts

001 010 100 1000 10000 100000T90 (s)

Figure 2 Distribution of GRB durations (11987990) of 953 bursts in theFermi-GBM (50ndash300 keV energy range) Taken from the 2nd Fermicatalog [23] 159 (17) of the bursts are ldquoshortrdquo

a b c d e

00 3

677

158

547

1008

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)

(Cou

nts

bin)GBM NaI3 + NaI4

(8keVndash260keV)

GBM BGO0(260keVndash5MeV)

LAT(no selection)

LAT(gt100MeV)

LAT(gt1GeV)

minus20 0 20 40 60 80 100Time since trigger (s)

Time since trigger (s)

150010005000

150010005000

4002000

3002001000

3002001000

5

0

3210

3000200010000

1000

500

0

6004002000

151050

6420

0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

151

050

10

5

0

400

200

0(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

Figure 3 Light curves for GRB 080916C observed with the GBMand the LAT detectors on board the Fermi satellite from lowest tohighest energies The top graph shows the sum of the counts in the8 to 260 keV energy band of two NaI detectors The second is thecorresponding plot for BGOdetector 0 between 260 keV and 5MeVThe third shows all LAT events passing the onboard event filter forgamma-rays (Insets) Views of the first 15 s from the trigger timeIn all cases the bin width is 05 s the per-second counting rate isreported on the right for convenience Taken from Abdo et al [57]

Already in the BATSE era several bursts were foundto have ldquoultra-longrdquo duration having 11987990 exceeding sim103 s(eg [58 59]) Recently several additional bursts were foundin this category (eg GRB 091024A GRB 101225A GRB111209A GRB 121027A and GRB 130925A [18 60ndash63])which raise the idea of a new class of GRBs If these burstsindeed represent a separate class they may have a different

progenitor than that of ldquoregularrdquo long GRBs [62 64 65]However recent analysis showed that bursts with duration11987990 sim 103 s need not belong to a special population whilebursts with 11987990 ≳ 104 s may belong to a separate population[66 67] As the statistics is very low my view is that this isstill an open issue

22 Spectral Properties

221 AWord of Caution Since this is a rapidly evolving fieldone has to be extra careful in describing the spectra of GRBprompt emission As I will show below the observed spectrais in fact sensitive to the analysis method chosen Thusbefore describing the spectra one has to describe the analysismethod

Typically the spectral analysis is based on analyzing fluxintegrated over the entire duration of the prompt emissionnamely the spectra is time-integrated Clearly this is a tradeoff as enough photons need to be collected in order to analyzethe spectra For weak bursts this is the only thing one cando However there is a major drawback here use of the timeintegrated spectra implies that important time-dependentsignals could potentially be lost or at least smeared This caneasily lead to the wrong theoretical interpretation

A second point of caution is the analysis method whichis done by a forward folding technique This means thefollowing First a model spectrum is chosen Second thechosen model is convolved with the detector response andcompared to the detected counts spectrumThird the modelparameters are varied in search for the minimal differencebetween model and data The outcome is the best fittedparameters within the framework of the chosen model Thisanalysis method is the only one that can be used due to thenonlinearity of the detectorrsquos response matrix which makesit impossible to invert

However the need to predetermine the fitted modelimplies that the results are biased by the initial hypothesisTwo different models can fit the data equally well This factwhich is often being ignored by theoreticians is importantto realize when the spectral fits are interpreted Key spectralproperties such as the energy of the spectral peak put strongconstraints on possible emission models Below I show a fewexamples of different analysis methods of the same data thatresult in different spectral peak energies slopes and so forthand therefore lead to different theoretical interpretations

222 The ldquoBandrdquo Model In order to avoid biases towards apreferred physical emission model GRB spectra are tradi-tionally fitted with a mathematical function which is knownas the ldquoBandrdquo function (after the late David Band) [68] Thisfunction had become the standard in this field and is oftenreferred to as ldquoBand modelrdquo The photon number spectra inthis model are given by

119873ph (119864)

= 119860

(

119864

100 keV)

120572

exp(minus 119864

1198640) 119864 lt (120572 minus 120573) 1198640

[

(120572 minus 120573) 1198640100 keV

]

120572minus120573

exp (120573 minus 120572) ( 119864

100 keV)

120573

119864 ge (120572 minus 120573) 1198640

(1)

Advances in Astronomy 5

NaI_03NaI_04

BGO_00LAT

Rate

(cou

ntss

minus1

keVminus1 )

420

minus2minus4

101 102 103 104 105 106 107

Energy (keV)

120590

100

10minus2

10minus4

10minus6

10minus8

(a)

103

102

10

ad

c

b

e

Energy (keV)10 102 103 104 105 106 107

F

(keV

cm

2 s)

(b)

Figure 4 Spectra of GRB 080916C at the five time intervals (andashe) defined in Figure 3 are fitted with a ldquoBandrdquo function (a) Count spectrumfor NaI BGO and LAT in time bin b (b) The model spectra in ]119865] units for all five time intervals in which a flat spectrum would indicateequal energy per decade of photon energy and the changing shapes show the evolution of the spectrum over time The ldquobroken power lawrdquofigure adopted from Abdo et al [57]

This model thus has 4 free parameters low energy spectralslope120572 high energy spectral slope120573 break energyasymp 119864

0 and

an overall normalization 119860 It is found that such a simplisticmodel which resembles a ldquobroken power lawrdquo is capableof providing good fits to many different GRB spectra seeFigure 4 for an example Thus this model is by far the mostwidely used in describing GRB spectra

Some variations of this model have been introduced inthe literature Examples are single power law (PL) ldquosmoothbroken power lawrdquo (SBPL) or ldquoComptonizedmodelrdquo (Comp)(see eg [69ndash72]) These are very similar in nature and donot in general provide a better physical insight

On the downside clearly having only 4 free parametersthis model is unable to capture complex spectral behaviorthat is known now to exist such as the different temporalbehavior of the high energy emission discussed above Evenmore importantly as will be discussed below the limitednumber of freemodel parameters in thismodel can easily leadto wrong conclusions Furthermore this model on purposeis mathematical in nature and therefore fitting the data withthis model does not by itself provide any clue about thephysical origin of the emission In order to obtain such aninsight one has to compare the fitted results to the predictionsof different theoretical models

When using the ldquoBandrdquo model to fit a large number ofbursts the distribution of the key model parameters (thelow and high energy slopes 120572 and 120573 and the peak energy119864peak) is shown to be surprisingly narrow (see Figure 5)The spectral properties of the two categories short and longGRBs detected by both BATSE Integral as well as Fermiare very similar with only minor differences [25 69 71ndash76] The low energy spectral slope is roughly in the rangeminus15 lt 120572 lt 0 averaging at ⟨120572⟩ ≃ minus1 The distribution of

the high energy spectral slope peaks at ⟨120573⟩ ≃ minus2 While typ-ically 120573 lt minus13 many bursts show a very steep 120573 consistentwith an exponential cutoff The peak energy averages around⟨119864peak⟩ ≃ 200 keV and it ranges from tens keV up to simMeV(and even higher in a few rare exceptional bursts)

As can be seen in Figures 4 and 5 the ldquoBandrdquo fits to thespectra have three key spectral properties (1) The promptemission extends to very high energies ≳MeVThis energy isabove the threshold for pair production (119898

119890= 0511MeV)

which is the original motivation for relativistic expansionof GRB outflows (see below) (2) The ldquoBandrdquo fits do notresemble a ldquoPlanckrdquo function hence the reason why thermalemission which was initially suggested as the origin of GRBprompt spectra [77 78] was quickly abandoned and notconsidered as a valid radiation process for a long time (3)Thevalues of the free ldquoBandrdquomodel parameters and in particularthe value of the low energy spectral slope 120572 are not easilyfitted with any simply broadband radiative process such assynchrotron or synchrotron self-Compton (SSC) Althoughin some bursts synchrotron emission could be used to fitthe spectra (eg [79ndash82]) this is not the case in the vastmajority of GRBs [83ndash86] This was noted already in 1998with the term ldquosynchrotron line of deathrdquo coined by Preeceet al [84] to emphasise the inability of the synchrotronemission model to provide good fits to the spectra of (most)GRBs

Indeed these three observational properties introduce amajor theoretical challenge as currently no simple physicallymotivatedmodel is able to provide convincing explanation tothe observed spectra However as already discussed abovethe ldquoBandrdquo fits suffer from several inherent major drawbacksand therefore the obtained results must be treated with greatcare

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 3

150

100

50

0minus5 60 minus5 40

Time (s)50

Time (s) Time (s)

minus5 20Time (s)

minus20 80 minus2 8

minus5 20

Time (s)

minus2 40 minus2 50

minus2 50

minus5 100

50 300Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

Time (s)

20

15

10

5

0

20

15

10

5

0

30

25

20

15

10

5

0

18

16

14

12

10

8

6

12

10

8

6

4

2

2

400

300

200

100

0

9

8

7

6

5

4

3

6

5

4

3

100

80

60

40

20

0

12

10

8

6

4

2

150

100

50

0

GRB 910503Trig 143

GRB 910711Trig 512

GRB 920216BTrig 1406

GRB 920221Trig 1425

GRB 921003ATrig 1974

GRB 921022BTrig 1997

GRB 921123ATrig 2067

GRB 930131ATrig 2151

GRB 931008CTrig 2571

GRB 940210Trig 2812

GRB 990316ATrig 7475

GRB 991216Trig 7906

Figure 1 Light curves of 12 bright gamma-ray bursts detected by BATSE Gamma-ray bursts light curves display a tremendous amount ofdiversity and few discernible patterns This sample includes short events and long events (duration ranging from milliseconds to minutes)events with smooth behavior and single peaks and events with highly variable erratic behavior with many peaks Created by Daniel Perleywith data from the public BATSE archive (httpgammaraymsfcnasagovbatsegrbcatalog)

(or physical origin) In addition there have been severalclaims for a small third class of ldquointermediaterdquo GRBs with11987990 sim 2 s [50ndash53] but this is still controversial (eg [48 54])

To further add to the confusion the light curve itselfvaries with energy band (eg Figure 3) One of Fermirsquos mostimportant results tomy view is the discovery that the highest

energy photons (in the LAT band) are observed to both (I)lag behind the emission at lower energies and (II) last longerBoth these results are seen in Figure 3 Similarly the widthof individual pulses is energy dependent It was found thatthe pulse width 120596 varies with energy 120596(119864) prop 119864

minus120572 with120572 sim 03ndash04 [55 56]

4 Advances in Astronomy

0

50

100

150

Num

ber o

f bur

sts

001 010 100 1000 10000 100000T90 (s)

Figure 2 Distribution of GRB durations (11987990) of 953 bursts in theFermi-GBM (50ndash300 keV energy range) Taken from the 2nd Fermicatalog [23] 159 (17) of the bursts are ldquoshortrdquo

a b c d e

00 3

677

158

547

1008

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)

(Cou

nts

bin)GBM NaI3 + NaI4

(8keVndash260keV)

GBM BGO0(260keVndash5MeV)

LAT(no selection)

LAT(gt100MeV)

LAT(gt1GeV)

minus20 0 20 40 60 80 100Time since trigger (s)

Time since trigger (s)

150010005000

150010005000

4002000

3002001000

3002001000

5

0

3210

3000200010000

1000

500

0

6004002000

151050

6420

0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

151

050

10

5

0

400

200

0(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

Figure 3 Light curves for GRB 080916C observed with the GBMand the LAT detectors on board the Fermi satellite from lowest tohighest energies The top graph shows the sum of the counts in the8 to 260 keV energy band of two NaI detectors The second is thecorresponding plot for BGOdetector 0 between 260 keV and 5MeVThe third shows all LAT events passing the onboard event filter forgamma-rays (Insets) Views of the first 15 s from the trigger timeIn all cases the bin width is 05 s the per-second counting rate isreported on the right for convenience Taken from Abdo et al [57]

Already in the BATSE era several bursts were foundto have ldquoultra-longrdquo duration having 11987990 exceeding sim103 s(eg [58 59]) Recently several additional bursts were foundin this category (eg GRB 091024A GRB 101225A GRB111209A GRB 121027A and GRB 130925A [18 60ndash63])which raise the idea of a new class of GRBs If these burstsindeed represent a separate class they may have a different

progenitor than that of ldquoregularrdquo long GRBs [62 64 65]However recent analysis showed that bursts with duration11987990 sim 103 s need not belong to a special population whilebursts with 11987990 ≳ 104 s may belong to a separate population[66 67] As the statistics is very low my view is that this isstill an open issue

22 Spectral Properties

221 AWord of Caution Since this is a rapidly evolving fieldone has to be extra careful in describing the spectra of GRBprompt emission As I will show below the observed spectrais in fact sensitive to the analysis method chosen Thusbefore describing the spectra one has to describe the analysismethod

Typically the spectral analysis is based on analyzing fluxintegrated over the entire duration of the prompt emissionnamely the spectra is time-integrated Clearly this is a tradeoff as enough photons need to be collected in order to analyzethe spectra For weak bursts this is the only thing one cando However there is a major drawback here use of the timeintegrated spectra implies that important time-dependentsignals could potentially be lost or at least smeared This caneasily lead to the wrong theoretical interpretation

A second point of caution is the analysis method whichis done by a forward folding technique This means thefollowing First a model spectrum is chosen Second thechosen model is convolved with the detector response andcompared to the detected counts spectrumThird the modelparameters are varied in search for the minimal differencebetween model and data The outcome is the best fittedparameters within the framework of the chosen model Thisanalysis method is the only one that can be used due to thenonlinearity of the detectorrsquos response matrix which makesit impossible to invert

However the need to predetermine the fitted modelimplies that the results are biased by the initial hypothesisTwo different models can fit the data equally well This factwhich is often being ignored by theoreticians is importantto realize when the spectral fits are interpreted Key spectralproperties such as the energy of the spectral peak put strongconstraints on possible emission models Below I show a fewexamples of different analysis methods of the same data thatresult in different spectral peak energies slopes and so forthand therefore lead to different theoretical interpretations

222 The ldquoBandrdquo Model In order to avoid biases towards apreferred physical emission model GRB spectra are tradi-tionally fitted with a mathematical function which is knownas the ldquoBandrdquo function (after the late David Band) [68] Thisfunction had become the standard in this field and is oftenreferred to as ldquoBand modelrdquo The photon number spectra inthis model are given by

119873ph (119864)

= 119860

(

119864

100 keV)

120572

exp(minus 119864

1198640) 119864 lt (120572 minus 120573) 1198640

[

(120572 minus 120573) 1198640100 keV

]

120572minus120573

exp (120573 minus 120572) ( 119864

100 keV)

120573

119864 ge (120572 minus 120573) 1198640

(1)

Advances in Astronomy 5

NaI_03NaI_04

BGO_00LAT

Rate

(cou

ntss

minus1

keVminus1 )

420

minus2minus4

101 102 103 104 105 106 107

Energy (keV)

120590

100

10minus2

10minus4

10minus6

10minus8

(a)

103

102

10

ad

c

b

e

Energy (keV)10 102 103 104 105 106 107

F

(keV

cm

2 s)

(b)

Figure 4 Spectra of GRB 080916C at the five time intervals (andashe) defined in Figure 3 are fitted with a ldquoBandrdquo function (a) Count spectrumfor NaI BGO and LAT in time bin b (b) The model spectra in ]119865] units for all five time intervals in which a flat spectrum would indicateequal energy per decade of photon energy and the changing shapes show the evolution of the spectrum over time The ldquobroken power lawrdquofigure adopted from Abdo et al [57]

This model thus has 4 free parameters low energy spectralslope120572 high energy spectral slope120573 break energyasymp 119864

0 and

an overall normalization 119860 It is found that such a simplisticmodel which resembles a ldquobroken power lawrdquo is capableof providing good fits to many different GRB spectra seeFigure 4 for an example Thus this model is by far the mostwidely used in describing GRB spectra

Some variations of this model have been introduced inthe literature Examples are single power law (PL) ldquosmoothbroken power lawrdquo (SBPL) or ldquoComptonizedmodelrdquo (Comp)(see eg [69ndash72]) These are very similar in nature and donot in general provide a better physical insight

On the downside clearly having only 4 free parametersthis model is unable to capture complex spectral behaviorthat is known now to exist such as the different temporalbehavior of the high energy emission discussed above Evenmore importantly as will be discussed below the limitednumber of freemodel parameters in thismodel can easily leadto wrong conclusions Furthermore this model on purposeis mathematical in nature and therefore fitting the data withthis model does not by itself provide any clue about thephysical origin of the emission In order to obtain such aninsight one has to compare the fitted results to the predictionsof different theoretical models

When using the ldquoBandrdquo model to fit a large number ofbursts the distribution of the key model parameters (thelow and high energy slopes 120572 and 120573 and the peak energy119864peak) is shown to be surprisingly narrow (see Figure 5)The spectral properties of the two categories short and longGRBs detected by both BATSE Integral as well as Fermiare very similar with only minor differences [25 69 71ndash76] The low energy spectral slope is roughly in the rangeminus15 lt 120572 lt 0 averaging at ⟨120572⟩ ≃ minus1 The distribution of

the high energy spectral slope peaks at ⟨120573⟩ ≃ minus2 While typ-ically 120573 lt minus13 many bursts show a very steep 120573 consistentwith an exponential cutoff The peak energy averages around⟨119864peak⟩ ≃ 200 keV and it ranges from tens keV up to simMeV(and even higher in a few rare exceptional bursts)

As can be seen in Figures 4 and 5 the ldquoBandrdquo fits to thespectra have three key spectral properties (1) The promptemission extends to very high energies ≳MeVThis energy isabove the threshold for pair production (119898

119890= 0511MeV)

which is the original motivation for relativistic expansionof GRB outflows (see below) (2) The ldquoBandrdquo fits do notresemble a ldquoPlanckrdquo function hence the reason why thermalemission which was initially suggested as the origin of GRBprompt spectra [77 78] was quickly abandoned and notconsidered as a valid radiation process for a long time (3)Thevalues of the free ldquoBandrdquomodel parameters and in particularthe value of the low energy spectral slope 120572 are not easilyfitted with any simply broadband radiative process such assynchrotron or synchrotron self-Compton (SSC) Althoughin some bursts synchrotron emission could be used to fitthe spectra (eg [79ndash82]) this is not the case in the vastmajority of GRBs [83ndash86] This was noted already in 1998with the term ldquosynchrotron line of deathrdquo coined by Preeceet al [84] to emphasise the inability of the synchrotronemission model to provide good fits to the spectra of (most)GRBs

Indeed these three observational properties introduce amajor theoretical challenge as currently no simple physicallymotivatedmodel is able to provide convincing explanation tothe observed spectra However as already discussed abovethe ldquoBandrdquo fits suffer from several inherent major drawbacksand therefore the obtained results must be treated with greatcare

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

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ThermodynamicsJournal of

4 Advances in Astronomy

0

50

100

150

Num

ber o

f bur

sts

001 010 100 1000 10000 100000T90 (s)

Figure 2 Distribution of GRB durations (11987990) of 953 bursts in theFermi-GBM (50ndash300 keV energy range) Taken from the 2nd Fermicatalog [23] 159 (17) of the bursts are ldquoshortrdquo

a b c d e

00 3

677

158

547

1008

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)(C

ount

ss)

(Cou

nts

s)

(Cou

nts

bin)GBM NaI3 + NaI4

(8keVndash260keV)

GBM BGO0(260keVndash5MeV)

LAT(no selection)

LAT(gt100MeV)

LAT(gt1GeV)

minus20 0 20 40 60 80 100Time since trigger (s)

Time since trigger (s)

150010005000

150010005000

4002000

3002001000

3002001000

5

0

3210

3000200010000

1000

500

0

6004002000

151050

6420

0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

Time since trigger (s)0 5 10 15

151

050

10

5

0

400

200

0(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

(Cou

nts

bin)

Figure 3 Light curves for GRB 080916C observed with the GBMand the LAT detectors on board the Fermi satellite from lowest tohighest energies The top graph shows the sum of the counts in the8 to 260 keV energy band of two NaI detectors The second is thecorresponding plot for BGOdetector 0 between 260 keV and 5MeVThe third shows all LAT events passing the onboard event filter forgamma-rays (Insets) Views of the first 15 s from the trigger timeIn all cases the bin width is 05 s the per-second counting rate isreported on the right for convenience Taken from Abdo et al [57]

Already in the BATSE era several bursts were foundto have ldquoultra-longrdquo duration having 11987990 exceeding sim103 s(eg [58 59]) Recently several additional bursts were foundin this category (eg GRB 091024A GRB 101225A GRB111209A GRB 121027A and GRB 130925A [18 60ndash63])which raise the idea of a new class of GRBs If these burstsindeed represent a separate class they may have a different

progenitor than that of ldquoregularrdquo long GRBs [62 64 65]However recent analysis showed that bursts with duration11987990 sim 103 s need not belong to a special population whilebursts with 11987990 ≳ 104 s may belong to a separate population[66 67] As the statistics is very low my view is that this isstill an open issue

22 Spectral Properties

221 AWord of Caution Since this is a rapidly evolving fieldone has to be extra careful in describing the spectra of GRBprompt emission As I will show below the observed spectrais in fact sensitive to the analysis method chosen Thusbefore describing the spectra one has to describe the analysismethod

Typically the spectral analysis is based on analyzing fluxintegrated over the entire duration of the prompt emissionnamely the spectra is time-integrated Clearly this is a tradeoff as enough photons need to be collected in order to analyzethe spectra For weak bursts this is the only thing one cando However there is a major drawback here use of the timeintegrated spectra implies that important time-dependentsignals could potentially be lost or at least smeared This caneasily lead to the wrong theoretical interpretation

A second point of caution is the analysis method whichis done by a forward folding technique This means thefollowing First a model spectrum is chosen Second thechosen model is convolved with the detector response andcompared to the detected counts spectrumThird the modelparameters are varied in search for the minimal differencebetween model and data The outcome is the best fittedparameters within the framework of the chosen model Thisanalysis method is the only one that can be used due to thenonlinearity of the detectorrsquos response matrix which makesit impossible to invert

However the need to predetermine the fitted modelimplies that the results are biased by the initial hypothesisTwo different models can fit the data equally well This factwhich is often being ignored by theoreticians is importantto realize when the spectral fits are interpreted Key spectralproperties such as the energy of the spectral peak put strongconstraints on possible emission models Below I show a fewexamples of different analysis methods of the same data thatresult in different spectral peak energies slopes and so forthand therefore lead to different theoretical interpretations

222 The ldquoBandrdquo Model In order to avoid biases towards apreferred physical emission model GRB spectra are tradi-tionally fitted with a mathematical function which is knownas the ldquoBandrdquo function (after the late David Band) [68] Thisfunction had become the standard in this field and is oftenreferred to as ldquoBand modelrdquo The photon number spectra inthis model are given by

119873ph (119864)

= 119860

(

119864

100 keV)

120572

exp(minus 119864

1198640) 119864 lt (120572 minus 120573) 1198640

[

(120572 minus 120573) 1198640100 keV

]

120572minus120573

exp (120573 minus 120572) ( 119864

100 keV)

120573

119864 ge (120572 minus 120573) 1198640

(1)

Advances in Astronomy 5

NaI_03NaI_04

BGO_00LAT

Rate

(cou

ntss

minus1

keVminus1 )

420

minus2minus4

101 102 103 104 105 106 107

Energy (keV)

120590

100

10minus2

10minus4

10minus6

10minus8

(a)

103

102

10

ad

c

b

e

Energy (keV)10 102 103 104 105 106 107

F

(keV

cm

2 s)

(b)

Figure 4 Spectra of GRB 080916C at the five time intervals (andashe) defined in Figure 3 are fitted with a ldquoBandrdquo function (a) Count spectrumfor NaI BGO and LAT in time bin b (b) The model spectra in ]119865] units for all five time intervals in which a flat spectrum would indicateequal energy per decade of photon energy and the changing shapes show the evolution of the spectrum over time The ldquobroken power lawrdquofigure adopted from Abdo et al [57]

This model thus has 4 free parameters low energy spectralslope120572 high energy spectral slope120573 break energyasymp 119864

0 and

an overall normalization 119860 It is found that such a simplisticmodel which resembles a ldquobroken power lawrdquo is capableof providing good fits to many different GRB spectra seeFigure 4 for an example Thus this model is by far the mostwidely used in describing GRB spectra

Some variations of this model have been introduced inthe literature Examples are single power law (PL) ldquosmoothbroken power lawrdquo (SBPL) or ldquoComptonizedmodelrdquo (Comp)(see eg [69ndash72]) These are very similar in nature and donot in general provide a better physical insight

On the downside clearly having only 4 free parametersthis model is unable to capture complex spectral behaviorthat is known now to exist such as the different temporalbehavior of the high energy emission discussed above Evenmore importantly as will be discussed below the limitednumber of freemodel parameters in thismodel can easily leadto wrong conclusions Furthermore this model on purposeis mathematical in nature and therefore fitting the data withthis model does not by itself provide any clue about thephysical origin of the emission In order to obtain such aninsight one has to compare the fitted results to the predictionsof different theoretical models

When using the ldquoBandrdquo model to fit a large number ofbursts the distribution of the key model parameters (thelow and high energy slopes 120572 and 120573 and the peak energy119864peak) is shown to be surprisingly narrow (see Figure 5)The spectral properties of the two categories short and longGRBs detected by both BATSE Integral as well as Fermiare very similar with only minor differences [25 69 71ndash76] The low energy spectral slope is roughly in the rangeminus15 lt 120572 lt 0 averaging at ⟨120572⟩ ≃ minus1 The distribution of

the high energy spectral slope peaks at ⟨120573⟩ ≃ minus2 While typ-ically 120573 lt minus13 many bursts show a very steep 120573 consistentwith an exponential cutoff The peak energy averages around⟨119864peak⟩ ≃ 200 keV and it ranges from tens keV up to simMeV(and even higher in a few rare exceptional bursts)

As can be seen in Figures 4 and 5 the ldquoBandrdquo fits to thespectra have three key spectral properties (1) The promptemission extends to very high energies ≳MeVThis energy isabove the threshold for pair production (119898

119890= 0511MeV)

which is the original motivation for relativistic expansionof GRB outflows (see below) (2) The ldquoBandrdquo fits do notresemble a ldquoPlanckrdquo function hence the reason why thermalemission which was initially suggested as the origin of GRBprompt spectra [77 78] was quickly abandoned and notconsidered as a valid radiation process for a long time (3)Thevalues of the free ldquoBandrdquomodel parameters and in particularthe value of the low energy spectral slope 120572 are not easilyfitted with any simply broadband radiative process such assynchrotron or synchrotron self-Compton (SSC) Althoughin some bursts synchrotron emission could be used to fitthe spectra (eg [79ndash82]) this is not the case in the vastmajority of GRBs [83ndash86] This was noted already in 1998with the term ldquosynchrotron line of deathrdquo coined by Preeceet al [84] to emphasise the inability of the synchrotronemission model to provide good fits to the spectra of (most)GRBs

Indeed these three observational properties introduce amajor theoretical challenge as currently no simple physicallymotivatedmodel is able to provide convincing explanation tothe observed spectra However as already discussed abovethe ldquoBandrdquo fits suffer from several inherent major drawbacksand therefore the obtained results must be treated with greatcare

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

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Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 5

NaI_03NaI_04

BGO_00LAT

Rate

(cou

ntss

minus1

keVminus1 )

420

minus2minus4

101 102 103 104 105 106 107

Energy (keV)

120590

100

10minus2

10minus4

10minus6

10minus8

(a)

103

102

10

ad

c

b

e

Energy (keV)10 102 103 104 105 106 107

F

(keV

cm

2 s)

(b)

Figure 4 Spectra of GRB 080916C at the five time intervals (andashe) defined in Figure 3 are fitted with a ldquoBandrdquo function (a) Count spectrumfor NaI BGO and LAT in time bin b (b) The model spectra in ]119865] units for all five time intervals in which a flat spectrum would indicateequal energy per decade of photon energy and the changing shapes show the evolution of the spectrum over time The ldquobroken power lawrdquofigure adopted from Abdo et al [57]

This model thus has 4 free parameters low energy spectralslope120572 high energy spectral slope120573 break energyasymp 119864

0 and

an overall normalization 119860 It is found that such a simplisticmodel which resembles a ldquobroken power lawrdquo is capableof providing good fits to many different GRB spectra seeFigure 4 for an example Thus this model is by far the mostwidely used in describing GRB spectra

Some variations of this model have been introduced inthe literature Examples are single power law (PL) ldquosmoothbroken power lawrdquo (SBPL) or ldquoComptonizedmodelrdquo (Comp)(see eg [69ndash72]) These are very similar in nature and donot in general provide a better physical insight

On the downside clearly having only 4 free parametersthis model is unable to capture complex spectral behaviorthat is known now to exist such as the different temporalbehavior of the high energy emission discussed above Evenmore importantly as will be discussed below the limitednumber of freemodel parameters in thismodel can easily leadto wrong conclusions Furthermore this model on purposeis mathematical in nature and therefore fitting the data withthis model does not by itself provide any clue about thephysical origin of the emission In order to obtain such aninsight one has to compare the fitted results to the predictionsof different theoretical models

When using the ldquoBandrdquo model to fit a large number ofbursts the distribution of the key model parameters (thelow and high energy slopes 120572 and 120573 and the peak energy119864peak) is shown to be surprisingly narrow (see Figure 5)The spectral properties of the two categories short and longGRBs detected by both BATSE Integral as well as Fermiare very similar with only minor differences [25 69 71ndash76] The low energy spectral slope is roughly in the rangeminus15 lt 120572 lt 0 averaging at ⟨120572⟩ ≃ minus1 The distribution of

the high energy spectral slope peaks at ⟨120573⟩ ≃ minus2 While typ-ically 120573 lt minus13 many bursts show a very steep 120573 consistentwith an exponential cutoff The peak energy averages around⟨119864peak⟩ ≃ 200 keV and it ranges from tens keV up to simMeV(and even higher in a few rare exceptional bursts)

As can be seen in Figures 4 and 5 the ldquoBandrdquo fits to thespectra have three key spectral properties (1) The promptemission extends to very high energies ≳MeVThis energy isabove the threshold for pair production (119898

119890= 0511MeV)

which is the original motivation for relativistic expansionof GRB outflows (see below) (2) The ldquoBandrdquo fits do notresemble a ldquoPlanckrdquo function hence the reason why thermalemission which was initially suggested as the origin of GRBprompt spectra [77 78] was quickly abandoned and notconsidered as a valid radiation process for a long time (3)Thevalues of the free ldquoBandrdquomodel parameters and in particularthe value of the low energy spectral slope 120572 are not easilyfitted with any simply broadband radiative process such assynchrotron or synchrotron self-Compton (SSC) Althoughin some bursts synchrotron emission could be used to fitthe spectra (eg [79ndash82]) this is not the case in the vastmajority of GRBs [83ndash86] This was noted already in 1998with the term ldquosynchrotron line of deathrdquo coined by Preeceet al [84] to emphasise the inability of the synchrotronemission model to provide good fits to the spectra of (most)GRBs

Indeed these three observational properties introduce amajor theoretical challenge as currently no simple physicallymotivatedmodel is able to provide convincing explanation tothe observed spectra However as already discussed abovethe ldquoBandrdquo fits suffer from several inherent major drawbacksand therefore the obtained results must be treated with greatcare

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

6 Advances in Astronomy

00 1

20

40

60

80

100

120

Band 120572minus3 minus2 minus1

(a)

0

20

40

60

80

100

10 100 1000 10000Band Epeak (keV)

(b)

AllGood

0

20

40

60

80

100

Band 120573minus6 minus5 minus4 minus3 minus2 minus1

(c)

Figure 5 Histograms of the distributions of ldquoBandrdquo model free parameters the low energy slope 120572 (a) peak energy 119864peak (b) and the highenergy slope 120573 (c) The data represent 3800 spectra derived from 487 GRBs in the first FERMI-GBM catalogueThe difference between solidand dashed curves is the goodness of fits the solid curve represent fits which were done under minimum 120594

2 criteria and the dash curves arefor all GRBs in the catalogue Figure adopted from Goldstein et al [71]

223 ldquoHybridrdquo Model An alternative model for fitting theGRB prompt spectra was proposed by Ryde [87 88] Beingaware of the limitations of the ldquoBandrdquomodel when analyzingBATSE data Ryde proposed a ldquohybridrdquo model that contains athermal component (a Planck function) and a single powerlaw to fit the nonthermal part of the spectra (presumablyresulting from Comptonization of the thermal photons)Rydersquos hybrid model thus contain four free parameters thesame number of free parameters as the ldquoBandrdquo model twoparameters fit the thermal part of the spectrum (temperatureand thermal flux) and two fit the nonthermal part Thusas opposed to the ldquoBandrdquo model which is mathematical innature Rydersquos model suggests a physical interpretation toat least part of the observed spectra (the thermal part) Anexample of the fit is shown in Figure 6

Clearly a single power law cannot be considered a validphysical model in describing the nonthermal part of thespectra as it diverges Nonetheless it can be acceptableapproximation when considering a limited energy range aswas available when analyzing BATSE data While the hybridmodel was able to provide comparable or even better fitswith respect to the ldquoBandrdquo model to several dozens brightGRBs [87ndash91] it was shown that this model overpredicts theflux at low energies (X-ray range) for many GRBs [92 93]This discrepancy however can easily be explained by theoversimplification of the use of a single power law as a wayto describe the nonthermal spectra both above and belowthe thermal peak From a physical perspective one expectsComptonization to modify the spectra above the thermalpeak but not below it see discussion below

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 7

100

10420

minus2100 1000

E (keV)

120590

EFE

(keV

cmminus2

sminus1 )

Trigger 0829 9

Figure 6 A ldquohybridrdquo model fit to the spectra of GRB 910927detected by BATSE Figure courtesy of Ryde

As Fermi enables a much broader spectral coveragethan BATSE in recent years Rydersquos hybrid model could beconfronted with data over a broader spectral range Indeedit was found that in several bursts (eg GRB090510 [94]GRB090902B [95ndash97] GRB110721A [98 99] GRB100724B[100] GRB100507 [101] or GRB120323A [102]) the broad-band spectra are best fitted with a combined ldquoBand +thermalrdquo model (see Figure 7) In these fits the peak of thethermal component is always found to be below the peakenergy of the ldquoBandrdquo part of the spectrum This is consistentwith the rising ldquosingle power lawrdquo that was used in fitting theband-limited nonthermal spectra

The ldquoBand + thermalrdquo model fits require six free param-eters as opposed to the four free parameters in both theldquoBandrdquo and in the original ldquohybridrdquo models While this isconsidered as a drawback this model has several notableadvantages First this model does not suffer from the energydivergence of a single power law fit as in Rydersquos originalproposal Second in comparison with ldquoBandrdquo model fits itshows significant improvement in quality both in statisticalerrors (reduced 120594

2) and even more importantly by thebehavior of the residuals when fitting the data with a ldquoBandrdquofunction often the residuals to the fit show a ldquowigglyrdquobehavior implying that they are not randomly distributedThis is solved when adding the thermal component to the fits

Similar to Rydersquos original model fits with ldquoBand +thermalrdquomodel can provide a physical explanation to only thethermal part of the spectra they still do not suggest physicalorigin to the nonthermal part of the spectra Nonetheless theaddition of the thermal part implies that the values of the freemodel parameters used in fitting the nonthermal part such asthe low energy spectral slope (120572) as well as the peak energy119864peak are different than the values that would have beenobtained by pure ldquoBandrdquo fits (namely without the thermal

BGO 1NaI 6NaI 7

NaI 9NaI 11LLE

1000

100

40

minus4

102101 103 104 105

Energy (keV)

Times 2176 2752 s

120590F

(k

eVc

msminus1 )

minus2

Figure 7 The spectra of GRB110721A are best fit with a ldquoBandrdquomodel (peaking at 119864peak sim 1MeV) and a blackbody component(having temperature 119879 sim 100 keV) The advantage over using justa ldquoBandrdquo function is evident when looking at the residuals (takenfrom Iyyani et al [99])

component see [102ndash105]) In some bursts the new valuesobtained are consistent with the predictions of synchrotrontheory suggesting a synchrotron origin of the nonthermalpart [106 107] However in many cases this interpretationis insufficient (eg [108]) see further discussion belowAnother (relativelyminor) drawback of these fits is that froma theoretical perspective even if a thermal component existsin the spectra it is expected to have the shape of a gray-body rather than a pure ldquoPlanckrdquo due to light aberration (seebelow)

One therefore concludes that the ldquoBand + thermalrdquo fitswhich became very popular recently can be viewed as anintermediate step towards full physically motivated fits of thespectraThey contain amix of a physicallymotivated part (thethermal part) with an addition mathematical function (theldquoBandrdquo part) whose physical origin still needs clarification

As of today pure ldquoPlanckrdquo spectral component is clearlyidentified in only a very small fraction of bursts Nonethelessthere is a good reason to believe that it is in fact veryubiquitous and that themain reason it is not clearly identifiedis due to its distortion A recent work [109] examined thewidth of the spectral peak quantified by 119882 the ratio ofenergies that define the full width half maximum (FWHM)The results of an analysis of over 2900 different BATSE andFermi bursts are shown in Figure 8 The smaller 119882 is thenarrower the spectral width is Imposed on the sample arethe line representing the spectral width from a pure ldquoPlanckrdquo(black) and a line representing the spectral width for slowcooling synchrotron (red) Fast cooling synchrotron resultsin much wider spectral width which would be shown to thefar right of this plot Thus while virtually all the spectralwidth is wider than ldquoPlanckrdquo over sim80 are narrower than

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

8 Advances in Astronomy

00 05 10 15 20 25 3000

05

10

15

20

Long GRBs

Sync

hrot

ron

Blac

kbod

y

Spectral width W (dex)

ΔNN

Figure 8 Full width half maximum of the spectral peaks of over2900 bursts fitted with the ldquoBandrdquo function The narrow mostspectra are compatible with a ldquoPlanckrdquo spectrum About sim80 ofthe spectra are too narrow to be fitted with the (slow cooling)synchrotron emission model (red line) When fast cooling is addednearly 100 of the spectra are too narrow to be compatible withthis model As it is physically impossible to narrow the broadbandsynchrotron spectra these results thus suggest that the spectral peakis due to some widening mechanism of the Planck spectrum whichare therefore pronounced (indirectly) in the vast majority of spectraFigure taken from Axelsson and Borgonovo [109]

what is allowed by the synchrotron model On the one handldquonarrowingrdquo a synchrotron spectra is (nearly) impossibleHowever there are various ways which will be discussedbelow in which pure ldquoPlanckrdquo spectra can be broadenedThus although ldquopurerdquo Planck is very rare these data suggestthat broadening of the ldquoPlanckrdquo spectra plays a major rolein shaping the spectral shape of the vast majority of GRBspectra

224 Time Resolved Spectral Analysis Rydersquos original anal-ysis is based on time resolved spectra The light curve iscut into time bins (having typical duration ≳1 s) and thespectra at each time bin are analyzed independently Thisapproach clearly limits the number of bursts that couldbe analyzed in this method to only the brightest onespresumably those showing smooth light curve over severaltens of seconds (namely mainly the long GRBs) However itsgreat advantage is that it enables detecting temporal evolutionin the properties of the fitted parameters in particular in thetemperature and flux of the thermal component

One of the key results of the analysis carried by Ryde andPersquoer [89] is the well defined temporal behavior of both thetemperature and flux of the thermal component Both thetemperature and flux evolve as a broken power law in time119879 prop 119905

120572 and 119865 prop 119905120573 with 120572 ≃ 0 and 120573 ≃ 06 at 119905 lt 119905brk asymp

few s and 120572 ≃ minus068 and 120573 ≃ minus2 at later times (see Figure 9)This temporal behavior was found among all sources inwhich thermal emission could be identified It may thereforeprovide a strong clue about the nature of the prompt emissionin at least those GRBs for which thermal component wasidentified To my personal view these findings may hold thekey to understanding the origin of the prompt emission andpossibly the nature of the progenitor

Due to Fermirsquos much greater sensitivity time resolvedspectral analysis is today in broad useThis enables observingtemporal evolution not only of the thermal component butof other parts of the spectra as well (see eg Figure 4) As anexample a recent analysis of GRB130427A reveals a temporalchange in the peak energy during the first 25 s of the burstwhich could be interpreted as being due to synchrotron origin[110]

225 Distinguished High Energy Component Prior to theFermi era time resolved spectral analysis was very difficultto conduct due to the relatively low sensitivity of the BATSEdetector and therefore its use was limited to bright GRBswith smooth light curve However Fermirsquos superb sensitivityenables carrying time resolved analysis to many more burstsOne of the findings is the delayed onset of GeV emissionwith respect to emission at lower energies which is seenin a substantial fraction of LAT bursts (see eg Figure 3)This delayed onset is further accompanied by a long livedemission (≳102 s) and separate light curve [57 95 111 112]The GeV emission decays as a power law in time 119871GeV prop

119905minus12 [113ndash115] Furthermore the GeV emission shows smoothdecay (see Figure 10) This behavior naturally points towardsa separate origin of the GeV and lower energy photons seediscussion below

Thus one can conclude that at this point in time (Dec2014) evidence exist for three separate components inGRB spectra (I) a thermal component peaking typicallyat sim100 keV (II) a nonthermal component whose origin isnot fully clear peaking at ≲MeV and lacking clear physicalpicture fitted with a ldquoBandrdquo function and (III) a thirdcomponent at very high energies (≳100MeV) showing aseparate temporal evolution [75 105]

Not all three components are clearly identified in allGRBs in fact separate evolution of the high energy partis observed in only a handful of GRBs The fraction ofGRBs which show clear evidence for the existence of athermal component is not fully clear it seems to dependon the brightness with bright GRBs more likely to showevidence for a thermal component (up to 50 of bright GRBsshow clear evidence for a separate thermal component ([105]and Larsson et al in prep)) Furthermore this fraction issensitive to the analysis method Thus final conclusions arestill lacking

Even more interestingly it is not at all clear that theldquobumprdquo identified as a thermal component is indeed suchsuch a bump could have other origins as well (see discussionbelow) Thus I think it is fair to claim that we are now in atransition phase on the one hand it is clear that fitting thedata with a pure ldquoBandrdquo model is insufficient and thus morecomplicated models which are capable of capturing moresubtle features of the spectra are being used On the otherhand these models are still not fully physically motivatedand thus a full physical insight of the origin of promptemission is still lacking

23 Polarization The leading models of the nonthermalemission namely synchrotron emission and Compton

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 9

Tem

pera

ture

kT o

b(k

eV)

1 10Time (s)

100

10

(a)

1 10Time (s)

Blac

kbod

y flu

xF B

B(e

rgc

m2 s

)

10minus6

10minus7

10minus8

(b)

Figure 9 (a) The temperature of the thermal component of GRB110721A at different time bins shows a clear ldquobroken power lawrdquo with119879(119905) sim 119905

minus025 before 119905brk sim 3 s and 119879(119905) sim 119905minus067 at later times (b) The flux of the thermal component shows a similar broken power law

temporal behavior with similar break time At late times 119865BB(119905) prop 119905minus2 See Ryde and Persquoer [89] for details Figure courtesy of Ryde

10000

1000

100

010

001

1000

100

010

001

01 10 100 1000 10000

01 10 100 1000

AGILE

T minus T (s)

Rate

(003ndash

03

GeV

)

Figure 10 Light curve of the emission ofGRB090510 above 100MeVextends to gt100 s and can be fitted with a smoothly broken powerlawThe times are scaled to the time119879⋆ = 06 s after theGBM triggerThe inset shows the AGILE light curve (energy range 30ndash300MeV)extending to much shorter times Figure taken fromGhirlanda et al[113]

scattering both produce highly polarized emission [118]Nonetheless due to the spherical assumption the inability tospatially resolve the sources and the fact that polarizationwasinitially discovered only during the afterglow phase [119 120]polarizationwas initially discussed only in the context ofGRBafterglow but not the prompt phase (eg [121ndash125])

The first claim of highly linearly polarized prompt emis-sion in a GRB Π = (80 plusmn 20) in GRB021206 byRHESSI [126] was disputed by a later analysis [127] A lateranalysis of BATSE data shows that the prompt emission ofGRB930131 and GRB96092 is consistent with having highlinear polarization Π gt 35 and Π gt 50 though the exactdegree of polarization could not be well constrained [128]Similarly Kalemci et al [129] McGlynn et al [130] and Gotzet al [131] showed that the prompt spectrum of GRB041219a

observed by Integral is consistent with being highly polarizedbut with no statistical significance

Recently high linear polarization Π = (27 plusmn 11)was observed in the prompt phase of GRB 100826a bythe GAP instrument on board IKAROS satellite [132] Asopposed to former measurements the significance level ofthis measurement is high 29120590 High linear polarizationdegree was further detected in GRB110301a (Π = 70 plusmn 22)with 37120590 confidence and in GRB100826a (Π = 84+16

minus28)with 33120590 confidence [133]

As of today there is no agreed theoretical interpretation tothe observed spectra (see discussion below) However differ-ent theoretical models predict different levels of polarizationwhich are correlated with the different spectra Thereforepolarization measurements have a tremendous potential inshedding new light on the different theoretical models andmay hold the key in discriminating between them

24 Emission at OtherWavebands Clearly the prompt emis-sion spectra are not necessarily limited to those wavebandsthat can be detected by existing satellites Although broad-band spectral coverage is important in providing clues to theorigin of the prompt emission and the nature of GRBs due totheir random nature and to the short duration it is extremelydifficult to observe the prompt emissionwithout fast accuratetriggering

As the physical origin of the prompt emission is not fullyclear it is difficult to estimate the flux at wavebands otherthan observed Naively the flux is estimated by interpolatingthe ldquoBandrdquo function to the required energy (eg [134])However as discussed above (and proved in the past) thismethod is misleading as (1) the ldquoBandrdquo model is a verycrude approximation to a more complicated spectra and(2) the values of the ldquoBandrdquo model low and high energyslopes change when new components are added Thus it

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

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[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

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[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

10 Advances in Astronomy

600

400

200

00 20 40 60 80

Time since BAT trigger (s)

30

20

10

0

Flux

den

sity

(Jy) 55

60

70

8090

Mag

nitu

de

Konu

s-w

ind

coun

t rat

e(c

ount

s per

64m

s)

(a)

RI

VBr

ROTSE V

5

10

15

20

25

Mag

nitu

de

101 102 103 104 105

Seconds after burst

times104

Flux

0 20 40 60 80 100

3

2

1

0

(b)

Figure 11 (a) Gamma-ray light curve (black) and optical data from ldquoPi in the skyrdquo (blue) and ldquoTortorardquo (red) of GRB080319B show how theoptical component traces the 120574-ray component Figure taken from Racusin et al [116] (b) Gamma-ray and optical light curve of GRB990123show that the optical light curve lags behind the 120574-rays Figure taken from Akerlof et al [117]

is of no surprise that early estimates were not matched byobservations

241 High Energy Counterpart At high energies there hasbeen one claim of possible TeV emission associated withGRB970417a [135] However since then no other confirmeddetections of high energy photons associated with any GRBprompt emission were reported Despite numerous attemptsonly upper limits on the very high energy flux were obtainedby the different detectors (MAGIC [136 137] MILAGRO(Milagro Collaboration [138]) HESS [139ndash141] VERITAS[142] and HAWC [143])

242 Optical Counterpart At lower energies (optic119883) therehave been several long GRBs for which a precursor (ora very long prompt emission duration) enabled fast slewof ground based robotic telescopes (andor Swift XRT andUVOT detectors) to the source during the prompt phaseThefirst ever detection of optical emission during the promptphase of a GRB was that of GRB990123 [117] Other examplesof optical detection are GRB041219A [144] GRB060124[145] GRB 061121 [146] the ldquonaked eyerdquo GRB080319B [116]GRB080603A [147] GRB080928 [148] GRB090727 [149]GRB121217a [150] GRB1304a7A [151] and GRB130925a [152]for a partial list

The results are diverse In some cases (eg GRB990123)the peak of the optical flux lags behind that of the 120574-ray fluxwhile in other GRBs (eg GRB080319B) no lag is observedThis is shown in Figure 11 Similarly while in some burstssuch as GRB080319B orGRB090727 the optical flux is severalorders of magnitude higher than that obtained by directinterpolation of the ldquoBandrdquo function from the X120574 ray bandin other bursts such as GRB080928 it seems to be fittedwell with a broken-power law extending at all energies (seeFigure 12) To further add to the confusion some GRBs show

complex temporal and spectral behavior in which the opticalflux and light curve changes its properties (with respect to theX120574 emission) with time Examples are GRB050820 [153] andGRB110205A [154]

These different properties hint towards different originof the optical emission It should be stressed that due to theobservational constraints optical counterparts are observedto date only in very longGRBs with typical11987990 of hundreds ofseconds (or more) Thus the optical emission may be viewedas part of the prompt phase but also as part of the earlyafterglow it may result from the reverse shock which takesplace during the early afterglow epoch See further discussionbelow

25 Correlations There have been several claims in the pastfor correlations between various observables of the promptGRB emission Clearly such correlations could potentiallybe extremely useful in both understanding the origin of theemission as well as the ability to use GRBs as probes forexample ldquostandard candlesrdquo similar to supernova Ia How-ever a word of caution is needed as already discussed manyof the correlations are based on values of fitted parameterssuch as 119864pk which are sensitive to the fitted model chosentypically the ldquoBandrdquo function As more refined models suchas the addition of a thermal component can change the peakenergy the claimed correlation may need to be modifiedSince final conclusion about the best physically motivatedmodel that can describe the prompt emission spectra has notemerged yet it is too early to know themodification that maybe required to the claimed correlations Similarly some ofthe correlations are based on the prompt emission durationwhich is ill-defined

The first correlation was found between the peak energy(identified as temperature) and luminosity of single pulseswithin the prompt emission [155] They found 119871 prop 119864

120572

peak

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 11

(Hz)1015 1017 1019 1021

Flux

den

sity

(mJy

)

104

103

102

10

1

01

10minus2 1 102 104

Energy (keV)

104

102

1

10minus2

Flux

den

sity

(keV

cmminus2

sminus1

keVminus1 )

(a)

1

2

3

4

5

7

00001

0001

01110100100010000

001 01 1 10 100

120582 (Aring)

E (keV)

1e minus 05

1e minus 06

1e minus 07

1e minus 08

1e minus 09

1e minus 10

F (Jy

)(b)

Figure 12 (a) The ldquoPi in the Skyrdquo and Konus-wind flux at 3 time intervals (fitted by a ldquoBandrdquo model) of GRB080319B The optical flux is2-3 orders of magnitude above the direct interpolation Figure taken from Racusin et al [116] (b) Combined UVOT and X120574 ray data ofGRB080928 at early times are fitted with a broken power law For this burst the slope is consistent with having synchrotron origin Figuretaken from Rossi et al [148]

with 120572 sim 16 These results were confirmed by Kargatis et al[156] though the errors on 120572 were large as 120572 ≃ 15ndash17

A similar correlation between the (redshift corrected)peak energy and the (isotropic equivalent) total gamma-rayenergy of different bursts was reported by Amati et al [157]namely 119864peak119911 prop 119864

120572

120574iso with 120572 sim 05 [157ndash159] Here119864peak119911 = 119864peak(1 + 119911) This became known as the ldquoAmatirelationrdquo

The Amati relation has been questioned by severalauthors claiming that it is an artifact of a selection effect orbiases (eg [160ndash166]) However counter arguments are thateven if such selection effects exist they cannot completelyexclude the correlation [167ndash171] To conclude it seem thatcurrent data (and analysis method) do support some corre-lation though with wide scatter This scatter still needs to beunderstood before the correlation could be used as a tool forexample for cosmological studies [172 173]

There are a few other notable correlations that were foundin recent years One is a correlation between the (redshiftcorrected) peak energy119864peak119911 and the isotropic luminosity in120574-rays at the peak flux 119871

120574peakiso [174 175] 119864peak119911 prop 119871052120574119901iso

A second correlation is between 119864peak119911 and the geometricallycorrected gamma-ray energy 119864

120574≃ (120579

21198952)119864120574iso where 120579119895 is

the jet opening angle (inferred from afterglow observations)119864peak119911 prop 119864

07120574

[176] It was argued that this relation is tighterthan the Amati relation however it relies on the correctinterpretation of breaks in the afterglow light curve to be

associated with jet breaks which can be problematic [177ndash181]

Several other proposed correlations exist I refer thereader to Kumar and Zhang [15] for a full list

3 Theoretical Framework

Perhaps the easiest way to understand the nature ofGRBs is tofollow the different episodes of energy conversion Althoughthe details of the energy transfer are still highly debatablethere is a wide agreement based on firm observationalevidence that there are several key episodes of energy conver-sion in GRBs (1) Initially a large amount of energy sim1053 ergor more is released in a very short time in a compactregion The source of this energy must be gravitational(2) Substantial part of this energy is converted into kineticenergy in the form of relativistic outflow This is the stagein which GRB jets are formed and accelerated to relativisticvelocities The exact nature of this acceleration process andin particular the role played by magnetic fields in it is stillnot fully clear (3) Part of this kinetic energy is dissipatedand is used in producing the gamma-rays that we observein the prompt emission Note that part of the observedprompt emission (the thermal part) may originate directlyfrom photons emitted during the initial explosion the energycarried by these photons is therefore not initially converted tokinetic form (4)The remaining of the kinetic energy (still inthe form of relativistic jet) runs into the interstellar medium

12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

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[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

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[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in Condensed Matter Physics

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

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Soft MatterJournal of

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12 Advances in Astronomy

Figure 13 Cartoon showing the basic ingredients of the GRBldquofireballrdquo model (1)The source of energy is a collapse of a massivestar (or merger of NS-NS or NS-BH not shown here) (2) Part ofthis energy is used in producing the relativistic jet This could bemediated by hot photons (ldquofireballrdquo) or by magnetic field (3) Thethermal photons decouple at the photosphere (4) Part of the jetkinetic energy is dissipated (by internal collisions in this picture)to produce the observed 120574 rays (5)The remaining kinetic energy isdeposited into the surrounding medium heating it and producingthe observed afterglow Cartoon is taken from Meszaros and Rees[17]

(ISM) and heats it producing the observed afterglow Thekinetic energy is thus gradually converted into heat and theafterglow gradually fades awayA cartoon showing these basicingredients in the context of the ldquofireballrdquo model is shown inFigure 13 adapted fromMeszaros and Rees [17]

31 Progenitors The key properties that are required fromGRB progenitors are (1) the ability to release a huge amountof energy sim1052-1053 erg (possibly even larger) within theobserved GRB duration of few seconds and (2) the abilityto explain the fast time variability observed 120575119905 ≳ 10minus3 simplying (via light crossing time argument) that the energysourcemust be compact119877 sim 119888120575119905 sim 300 km namely of stellarsize

While 20 years ago over hundred different models wereproposed in explaining possible GRB progenitors (see [182])natural selection (namely confrontation with observationsover the years) led to the survival of two main scenarios Thefirst is a merger of two neutron stars (NS-NS) or a blackhole and a neutron star (BH-NS) The occurrence rate andthe expected energy released sim119866119872

2119877 sim 1053 erg (using

119872 sim 119872⊙and 119877 ≳ 119877sch the Scharzschild radius of stellar-

size black hole) are sufficient for extragalactic GRBs [183ndash187]The alternative scenario is the core collapse of a massivestar accompanied by accretion into a black hole ([188ndash194]and references therein) In this scenario similar amountof energy up to sim1054 erg may be released by tapping therotational energy of a Kerr black hole formed in the corecollapse andor the inner layers of the accretion disk

The observational association of long GRBs to type Ibcsupernova discussed above as well as the time scale of thecollapse event ≲1 minute which is similar to that observedin long GRBs makes the core collapse or ldquocollapsarrdquo modelthe leading model for explaining long GRBs The mergerscenario on the other hand is currently the leading modelin explaining short GRBs (see eg discussions in [5 8 16])

32 Relativistic Expansion and Kinetic Energy DissipationThe ldquoFireballrdquo Model A GRB event is associated with acatastrophic energy release of a stellar size object The hugeamount of energy sim1052-1053 erg released in such a shorttime and compact volume results in a copious productionof neutrinos antineutrinos (initially in thermal equilibrium)and possible release of gravitational waves These two byfar the most dominant energy forms are yet not detected Asmaller fraction of the energy (of the order 10minus3-10minus2 of thetotal energy released) goes into high temperature (≳MeV)plasma containing photons 119890plusmn pairs and baryons knownas ldquofireballrdquo [195] The fireball may contain a comparable oreven larger amount of magnetic energy in which case it isPoynting flux dominated [196ndash201] (some authors use thephrase ldquocold fireballrdquo in describing magnetically dominatedejecta as opposed to ldquohot fireballsrdquo here I will simply use theterm ldquofireballrdquo regardless of the fraction of energy stored inthe magnetic field)

The scaling laws that govern the expansion of the fireballdepend on its magnetization Thus one must discriminatebetween photon-dominated (or magnetically-poor) outflowandmagnetic dominated outflow I discuss in this section thephoton-dominated one (ldquohot fireballrdquo) Magnetic dominatedoutflow (ldquocold fireballrdquo) will be discussed in the next section(Section 33)

321 Photon Dominated Outflow Let us consider firstphoton-dominated outflow In this model it is assumedthat a large fraction of the energy released during the col-lapsemerger is converted directly into photons close to the jetcore at radius 1199030 (which should be≳ the Schwarzschild radiusof the newly formed black hole) The photon temperature is

1198790 = (119871

412058711990320119888119886)

14

= 121198711452 119903minus1207 MeV (2)

where 119886 is the radiation constant 119871 is the luminosity and119876 = 10119909119876

119909in cgs units is used here and below This

temperature is above the threshold for pair productionimplying that a large number of 119890plusmn pairs are created viaphoton-photon interactions (and justifying the assumptionof full thermalization) The observed luminosity is manyorders of magnitude above the Eddington luminosity 119871

119864=

4120587119866119872119898119901119888120590119879= 125 times 1038(119872119872

⊙) erg sminus1 implying that

radiation pressure is much larger than self-gravity and thefireball must expand

Thedynamics of the expected relativistic fireball were firstinvestigated by Goodman [77] Paczynski [78] and ShemiandPiran [202]Theultimate velocity it will reach depends onthe amount of baryons (baryon load) within the fireball [184]which is uncertain The baryon load can be deduced fromobservations as the final expansion kinetic energy cannotexceed the explosion energy the highest Lorentz factor thatcan be reached is Γmax = 119864119872119888

2 Thus the fact that GRBsare known to have high bulk Lorentz factors Γ ≳ 102 atlater stages (during the prompt and afterglow emission) [203ndash212] implies that only a small fraction of the baryons in theprogenitor star(s) is in fact accelerated and reach relativisticvelocities

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

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Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

Advances in Astronomy 13

322 Scaling Laws for Relativistic Expansion InstantaneousEnergy Release The scaling laws for the fireball evolutionfollow conservation of energy and entropy Let us assume firstthat the energy release is ldquoinstantaneousrdquo namely within ashell of size 120575119903 sim 1199030 Thus the total energy contained withinthe shell (as seen by an observer outside the expanding shell)is

119864obprop Γ (119903)119881

10158401198791015840(119903)

4prop Γ (119903) 119903

2Γ (119903) 1199030119879

1015840(119903)

4= const (3)

Here 1198791015840(119903) is the shellrsquos comoving temperature and 1198811015840=

412058711990321205751199031015840 is its comoving volume Note that the first factorof Γ(119903) is needed in converting the comoving energy to theobserved energy and the second originates from transfor-mation of the shellrsquos width the shellrsquos comoving width (asmeasured by a comoving observer within it) is related to itswidth as measured in the lab frame (1199030) by 120575119903

1015840= Γ(119903)1199030

Starting from the fundamental thermodynamic relation119889119878 = (119889119880 + 119901119889119881)119879 one can write the entropy of a fluidcomponent with zero chemical potential (such as photonfluid) in its comoving frame 1198781015840 = 119881

1015840(1199061015840+ 1199011015840)1198791015840 Here

1199061015840 1199011015840 are the internal energy density and pressure measured

in the comoving frame For photons 1199011015840 = 11990610158403 prop 119879

10158404Since initially both the rest mass and energy of the baryonsare negligible the entropy is provided by the photons Thusconservation of entropy implies

1198781015840prop 11988110158401198791015840(119903)

3prop 119903

2Γ (119903) 1199030119879

1015840(119903)

3= const (4)

Dividing (3) and (4) one obtains Γ(119903)1198791015840(119903) = const fromwhich (using again these equations) one can write the scalinglaws of the fireball evolution

1198791015840(119903) prop 119903

minus1

Γ (119903) prop 119903

1198811015840(119903) prop 119903

3

(5)

As the shell accelerates the baryon kinetic energyΓ(119903)119872119888

2 increases until it becomes comparable to the totalfireball energy (the energy released in the explosion) at Γ =

Γmax ≃ 120578 at radius 119903119904sim 1205781199030 (assuming that the outflow is

still optically thick at 119903119904 and so the acceleration can continue

until this radius) Here 120578 equiv 1198641198721198882 is the specific entropy

per baryon Note that during the acceleration phase theshellrsquos kinetic energy increase comes at the expense of the(comoving) internal energy as is reflected by the fact that thecomoving temperature drops

Beyond the saturation radius 119903119904 most of the available

energy is in kinetic form and so the flow can no longeraccelerate and it coasts The spatial evolution of the Lorentzfactor is thus

Γ (119903) =

(

119903

1199030) 119903 ≲ 119903

119904

120578 119903 ≳ 119903119904

(6)

Equation (4) that describes conservation of (comoving)entropy holds in this regime as well therefore in the regime119903 gt 119903119904one obtains 11990321198791015840(119903)3 = const or

Γ (119903) = 120578

1198791015840(119903) prop 119903

minus23

1198811015840(119903) prop 119903

2

(7)

The observed temperature therefore evolves with radius as

119879ob(119903) = Γ (119903) 119879

1015840(119903) =

1198790 119903 lt 119903119904

1198790 times (119903

119903119904

)

minus23119903 gt 119903119904

(8)

323 Continuous Energy Release Let us assume next thatthe energy is released over a longer duration 119905 ≫ 1199030119888 (asis the case in long GRBs) In this scenario the progenitorcontinuously emits energy at a rate 119871 (ergs) and thisemission is accompanied bymass ejected at a rate = 119871120578119888

2The analysis carried above is valid for each fluid elementseparately provided that 119864 is replaced by 119871 and 119872 by and thus the scaling laws derived above for the evolution ofthe (average) Lorentz factor and temperature as a functionof radius hold However there are a few additions to thisscenario

We first note the following [1] The comoving numberdensity of baryons follows mass conservation

1198991015840

119901(119903) =

41205871199032119898119901119888Γ (119903)

=

119871

412058711990321198981199011198883120578Γ (119903)

(9)

(assuming spherical explosion) Below 119903119904 the (comov-

ing) energy density of each fluid element is relativistic1198861198791015840(119903)

41198991015840

1199011198981199011198882

= 120578(1199030119903) Thus the speed of sound inthe comoving frame is 119888

119904≃ 119888radic3 sim 119888 The time a fluid

element takes to expand to radius 119903 119903119888 in the observer framecorresponds to time 1199051015840 sim 119903Γ119888 in the comoving frame duringthis time sound waves propagate a distance 1199051015840119888

119904sim 119903119888Γ119888 =

119903Γ (in the comoving frame) which is equal to 119903Γ2 = 11990320119903

in the observer frame This implies that at the early stages ofthe expansion where 119903 ≳ 1199030 sound waves have enough timeto smooth spatial fluctuations on scale sim 1199030 On the otherhand regions separated by Δ119903 gt 1199030 cannot interact with eachother As a result fluctuations in the energy emission ratewould result in the ejection and propagation of a collectionof independent subshells each having typical thickness 1199030

Each fluid element may have a slightly different densityand thus have a slightly different terminal Lorentz factor thestandard assumption is 120575Γ sim 120578 This implies a velocity spread120575V = V1 minusV2 asymp 1198882120578

2 where 120578 is the characteristic value of theterminal Lorentz factor If such two fluid elements originatewithin a shell (of initial thickness 1199030) spreading between thesefluid elements will occur after typical time 119905spread = 1199030120575V andat radius (in the observerrsquos frame) [213]

119903spread = V2119905spread ≃ 1198881199030 (21205782

119888

) ≃ 212057821199030 (10)

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

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Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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AerodynamicsJournal of

Volume 2014

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PhotonicsJournal of

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Journal of

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ThermodynamicsJournal of

14 Advances in Astronomy

According to the discussion above this is also the typicalradius where two separate shells will begin to interact (some-times referred to as the ldquocollision radiusrdquo 119903col)

The spreading radius is a factor 120578 larger than the satura-tion radius Thus no internal collisions are expected duringthe acceleration phase namely at 119903 lt 119903

119904 Below the spreading

radius individual shellrsquos thickness (in the observerrsquos frame)120575119903 is approximately constant and equal to 1199030 At larger radii119903 gt 119903spread it becomes 120575119903 = 119903120575V119888 sim 1199031205782

Since the comoving radial width of each shell is 1205751199031015840 = Γ120575119903it can be written as

1205751199031015840sim

1199030Γ sim 119903 119903 lt 119903119904

1199030120578 119903119904lt 119903 lt 119903spread

119903

120578

119903 gt 119903spread

(11)

The comoving volume of each subshell 1198811015840 prop 11990321205751199031015840 is thus

1198811015840prop 119903

21205751199031015840sim

1199033

119903 lt 119903119904

1199030120578 1199032119903119904lt 119903 lt 119903spread

1199033

120578

119903 gt 119903spread

(12)

324 Internal Collisions as Possible Mechanism of KineticEnergy Dissipation At radii 119903 gt 119903spread = 119903coll spreadingwithin a single shell as well as interaction between two con-secutive shells becomes possible The idea of shell collisionwas suggested early on [214ndash218] as a way to dissipate the jetkinetic energy and convert it into the observed radiation

The key advantages of the internal collision model are (1)its simplicity it is a very straightforward idea that naturallyrises from the discussion above (2) it is capable of explainingthe rapid variability observed and (3) the internal collisionsare accompanied by (internal) shock waves It is believedthat these shock waves are capable of accelerating particles tohigh energies via Fermimechanism The energetic particlesin turn can emit the high-energy nonthermal photonsobserved for example via synchrotron emission Thus theinternal collisions is believed to be an essential part in thisenergy conversion chain that results in the production of 120574-rays

On the other hand the main drawbacks of the modelare (1) the very low efficiency of energy conversion (2)by itself the model does not explain the observed spectraonly suggests a way in which the kinetic energy can bedissipated In order to explain the observed spectra oneneeds to add further assumptions about how the dissipatedenergy is used in producing the photons (eg assumptionsabout particle acceleration etc) Furthermore as will bediscussed in Section 35 below it is impossible to explainthe observed spectra within the framework of this modelusing standard radiative processes (such as synchrotron emis-sion or Compton scattering) without invoking additionalassumptions external to it (3) lack of predictivity whileit does suggest a way of dissipating the kinetic energy itdoes not provide many details such as the time in which

dissipations are expected or the amount of energy that shouldbe dissipated in each collision (only rough limits) Thus itlacks a predictive power

The basic assumption is that at radius 119903coll = 119903spreadtwo shells collide This collision dissipates part of the kineticenergy and converts it into photons The time delay of theproduced photons (with respect to a hypothetical photonemitted at the center of expansion and travels directly towardsthe observer) is

120575119905ob≃

119903coll21205782119888

sim

1199030119888

(13)

namely of the same order as the central engine variabilitytime Thus this model is capable of explaining the rapid(≳1ms) variability observed

On the other hand this mechanism suffers a severeefficiency problem as only the differential kinetic energybetween two shells can be dissipated Consider for exampletwo shells of masses1198981 and1198982 and initial Lorentz factors Γ1and Γ2 undergoing plastic collision Conservation of energyand momentum implies that the final Lorentz factor of thecombined shell is [217]

Γ119891≃ (

1198981Γ1 + 1198982Γ21198981Γ1 + 1198982Γ2

)

12(14)

(assuming that both Γ1 Γ2 ≫ 1)The efficiency of kinetic energy dissipation is

120578 = 1minus(1198981 + 1198982) Γ119891

1198981Γ1 + 1198982Γ2

≃ 1minus 1198981 + 1198982

(11989821 + 119898

22 + 11989811198982 (Γ1Γ2 + Γ2Γ1))

12

(15)

Thus in order to achieve high dissipation efficiency oneideally requires similar masses 1198981 ≃ 1198982 and high contrastin Lorentz factors (Γ1Γ2) ≫ 1 Such high contrast is difficultto explain within the context of either the ldquocollapsarrdquo or theldquomergerrdquo progenitor scenarios

Even under these ideal conditions the combined shellrsquosLorentz factor Γ

119891 will be high therefore the contrast

between the Lorentz factors of a newly coming shell andthe merged shell in the next collision will not be as highAs a numerical example if the initial contrast is (Γ1Γ2) =

10 for 1198981 = 1198982 one can obtain high efficiency of ≳40however the efficiency of the next collision will drop to sim11When considering ensemble of colliding shells under variousassumptions of the ejection properties of the different shellstypical values of the global efficiency are of the order of1ndash10 [81 217 219ndash224] These values are in contrast toobservational evidence of a much higher efficiency of kineticenergy conversion during the prompt emission of the orderof tens of percents (sim50) which are inferred by estimatingthe kinetic energy using afterglow measurements [43 225ndash229]

While higher efficiency of energy conversion in internalshocks was suggested by a few authors [230 231] we pointout that these works assumed very large contrast in Lorentz

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

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International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

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Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

Advances in Astronomy 15

factors (Γ1Γ2) ≫ 10 for almost all collisions as discussedabove such a scenario is unlikely to be realistic within theframework of the known progenitor models

I further stress that the efficiency discussed in this sectionrefers only to the efficiency in dissipating the kinetic energyThere are a few more episodes of energy conversion thatare required before the dissipated energy is radiated as theobserved 120574-raysThese include (i) using the dissipated energyto accelerate the radiating particles (likely electrons) to highenergies (ii) converting the radiating particlersquos energy intophotons and (iii) finally the detectors being sensitive onlyover a limited energy band and thus part of the radiatedphotons cannot be detected Thus over all the measuredefficiency namely the energy of the observed 120574-ray photonsrelative to the kinetic energy is expected to be very low in thismodel inconsistent with observations

An alternative idea for kinetic energy dissipation arisesfrom the possibility that the jet composition may containa large number of free neutrons These neutrons that areproduced by dissociation of nuclei by 120574-ray photons in theinner regions decouple from the protons below the photo-sphere (see below) due to the lower cross section for proton-neutron collision relative to Thomson cross section [232ndash235] This leads to friction between protons and neutronsas they have different velocities which in turn results inproduction of 119890+ that follow the decay of pions (which areproduced themselves by 119901-119899 interactions) These positronsIC scatter the thermal photons producing 120574-ray radiationpeaking at simMeV [236] A similar result is obtained whennonzero magnetic fields are added in which case contribu-tion of synchrotron emission becomes comparable to that ofscattering the thermal photons [237]

325 Optical Depth and Photosphere During the initialstages of energy release a high temperature ≳ MeV (see(2)) ldquofireballrdquo is formed At such high temperature a largenumber of 119890plusmn pairs are produced [77 78 202] The photonsare scattered by these pairs and cannot escape However oncethe temperature drops to 1198791015840 ≲ 17 keV the pairs recombineand thereafter only a residual number of pairs are left in theplasma [78] Provided that 120578 ≲ 105 the density of residualpairs is much less than the density of ldquobaryonicrdquo electronsassociated with the protons 119899

119890= 119899119901 (A large number of pairs

may be produced later on when kinetic energy is dissipatedeg by shell collisions)This recombination typically happensat 119903 lt 119903

119904

Equation (9) thus provides a good approximation to thenumber density of both protons and electrons in the plasmaUsing this equation one can calculate the optical depth byintegrating the mean free path of photons emitted at radius119903 A 1-d calculation (namely photons emitted on the line ofsight) gives [184 238]

120591 = int

infin

119903

1198991015840

119890120590119879Γ (1minus120573) 1198891199031015840 ≃ 1198991015840

119890120590119879

119903

2Γ (16)

where120573 is the flow velocity and 120590119879isThomsonrsquos cross section

the use of this cross section is justified since in the comovingframe the photonrsquos temperature is 1198791015840 = 119879ob

Γ ≪ 1198981198901198882

The photospheric radius can be defined as the radius fromwhich 120591(119903ph) = 1

119903ph ≃120590119879

81205871199032119898119901119888Γ120578

=

119871120590119879

81205871198981199011198883Γ120578

2

≃ 2times 101111987152120578minus325 cm

(17)

In this calculation I assumed constant Lorentz factor Γ = 120578which is justified for 119903ph gt 119903

119904 In the case of fluctuative flow

resulting in shells 120578 represents an average value of the shellrsquosLorentz factor Further note that an upper limit on 120578 withinthe framework of thismodel is given by the requirement 119903ph gt119903119904rarr 120578 lt (119871120590

1198798120587119898

11990111988831199030) ≃ 1031198711452 119903

minus1407 This is because

as the photons decouple the plasma at the photosphere forlarger values of 120578 the acceleration cannot continue above 119903ph[239 240] In this scenario the observed spectra are expectedto be (quasi)thermal in contrast to the observations

The observed temperature at the photosphere is calcu-lated using (2) (8) and (17)

119879ob= 1198790 (

119903ph

119903119904

)

minus23=

80(1 + 119911)

119871minus51252 120578

8325 119903

1607 keV (18)

Similarly the observed thermal luminosity 119871obth prop 1199032Γ211987910158404prop

1199030 at 119903 lt 119903

119904and 119871obth prop 119903

minus23 at 119903 gt 119903119904[239] Thus

119871 th119871

≃ (

119903ph

119903119904

)

minus23= 66times 10minus2119871minus2352 120578

8325 119903

2307 (19)

Note the very strong dependence of the observed temperatureand luminosity on 120578 (here 119871 is the luminosity released in theexplosion the observed luminosity in 120574-rays is just a fractionof this luminosity)

The results of (19) show that the energy released asthermal photonsmay be a few of the explosion energyThisvalue is of the same order as the efficiency of the dissipationof kinetic energy via internal shocks However as discussedabove only a fraction of the kinetic energy dissipated viainternal shocks is eventually observed as photons while noadditional episodes of energy conversion (and losses) areadded to the result in (19) Furthermore the result in (19)is very sensitive to the uncertain value of 120578 via the ratio of(119903ph119903119904) for high 120578 119903ph is close to 119903

119904 reducing the adiabatic

losses and increasing the ratio of thermal luminosity In sucha scenario the internal shocks if occurring are likely to takeplace at 119903coll sim 120578119903

119904gt 119903ph namely in the optically thin region

I will discuss the consequences of this result in Section 353below

The calculation of the photospheric radius in (17) wasgeneralized by Persquoer [241] to include photons emitted off-axis in this case the term ldquophotospheric radiusrdquo should bereplaced with ldquophotospheric surfacerdquo which is the surface oflast scattering of photons before they decouple the plasmaSomewhat counterintuitively for a relativistic (Γ ≫ 1)spherical explosion this surface assumes a parabolic shapegiven by Persquoer [241]

119903ph (120579) ≃119877119889

2120587(

1Γ2 +

1205792

3) (20)

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

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[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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FluidsJournal of

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Advances in Condensed Matter Physics

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AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

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Statistical MechanicsInternational Journal of

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AstrophysicsJournal of

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 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

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ThermodynamicsJournal of

16 Advances in Astronomy

105

104

103

102

101

10minus6 10minus5 10minus4 10minus3 10minus2 10minus1 100

10minus1

100

Angle to the line of sight 120579

Nor

mal

ized

radi

usrr

0

Figure 14The green line represents the (normalized) photosphericradius 119903ph as a function of the angle to the line of sight 120579 for sphericalexplosion (see (20)) The red dots represent the last scatteringlocations of photons ejected in the center of relativistic expandingldquofireballrdquo (using a Monte-Carlo simulation) The black lines showcontours Clearly photons can undergo their last scattering at arange of radii and angles leading to the concept of ldquovague photo-sphererdquoThe observed photospheric signal is therefore smeared bothin time and energy Figure taken from Persquoer [241]

where119877119889equiv 120590

119879(4119898119901120573119888) depends on themass ejection rate

and velocityAn even closer inspection reveals that photons do not

necessarily decouple the plasma at the photospheric surfacethis surface of 120591(119903 120579) = 1 simply represents a probability of119890minus1 for a photon to decouple the plasma Instead the photonshave a finite probability of decoupling the plasma at everylocation in space This is demonstrated in Figure 14 adoptedfrom [241] This realization led Beloborodov to coin the termldquovague photosphererdquo [242]

The immediate implication of this nontrivial shape of thephotosphere is that the expected radiative signal emergingfrom the photosphere cannot have a pure ldquoPlanckrdquo shapebut is observed as a gray-body due to the different Dopplerboosts and different adiabatic energy losses of photons below119903ph [241 243] This is in fact the relativistic extension of theldquolimb darkeningrdquo effect known from stellar physics As will bediscussed in Section 354 below while in spherical outflowonly a moderate modification to a pure ldquoPlanckrdquo spectra isexpected this effect becomes extremely pronounced whenconsidering more realistic jet geometries and can in fact beused to study GRB jet geometries [244]

33 Relativistic Expansion of Magnetized Outflows

331TheMagnetarModel A second type of models assumesthat the energy released during the collapse (or the merger)is not converted directly into photon-dominated outflow butinstead is initially used in producing very strong magneticfields (Poynting flux dominated plasma) Only at a secondstage the energy stored in the magnetic field is used in both

accelerating the outflow to relativistic speeds (jet productionand acceleration) as well as heating the particles within thejet

There are a few motivations for considering this alterna-tive scenario Observationally one of the key discoveries ofthe Swift satellite is the existence of a long lasting ldquoplateaurdquoseen in the the early afterglow of GRBs at the X-ray band[227 245 246] This plateau is difficult to explain in thecontext of jet interaction with the environment but can beexplained by continuous central engine activity (though itmay be explained by other mechanisms eg reverse shockemission see [247 248]) A second motivation is the factthat magnetic fields are long thought to play a major role injet launching in other astronomical objects such as AGNsvia the Blandford-Znajek [249] or the Blandford-Payne [250]mechanisms These mechanisms have been recently testedand validated with state of the art numerical GR-MHDsimulations [251ndash260] see further explanations in [261] It isthus plausible that they may play some role in the context ofGRBs as well

The key idea is that the core collapse of the massive stardoes not form a black hole immediately but instead leadsto a rapidly rotating protoneutron star with a period ofsim1ms and very strong surface magnetic fields (119861 ≳ 1015 G)This is known as the ldquomagnetarrdquo model [197 262ndash266] Themaximum energy that can be stored in a rotating neutronstar is sim2 times 1052 erg and the typical timescale over which thisenergy can be extracted issim10 s (for this value of themagneticfield) These values are similar to the values observed in longGRBs The magnetic energy extracted drives a jet along thepolar axis of the neutron star [267ndash272] Following this mainenergy extraction residual rotational ormagnetic energymaycontinue to power late time flaring or afterglow emissionwhich may be the origin of the observed X-ray plateau [273]

332 Scaling Laws for Jet Acceleration inMagnetizedOutflowsExtraction of the magnetic energy leads to accelerationof particles to relativistic velocities The evolution of thehydrodynamic quantities in these Poynting-flux dominatedoutflow was considered by several authors [274ndash281] Thescaling laws of the acceleration can be derived by noting thatdue to the high baryon load ideal MHD limit can be assumed[274]

In this model there are two parts to the luminosity [275]a kinetic part 119871

119896= Γ119888

2 and a magnetic part 119871119872

=

41205871199032119888120573(11986124120587) where 120573 is the outflow velocity Thus 119871 =

119871119896+ 119871119872 Furthermore in this model throughout most of the

jet evolution the dominated component of the magnetic fieldis the toroidal component and so B perp 120573

An important physical quantity is the magnetizationparameter 120590 which is the ratio of Poynting flux to kineticenergy flux

120590 equiv

119871119872

119871119896

=

1198612

4120587Γ21198991198981199011198882 (21)

At the Alfven radius 1199030 (at 119903 = 1199030 the flow velocity is equal totheAlfven speed) the key assumption is that the flow is highlymagnetized and so the magnetization is 120590(1199030) equiv 1205900 ≫ 1

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 17

The magnetization plays a similar role to that of the baryonloading in the classical fireball model

The basic idea is that the magnetic field in the flowchanges polarity on a small scale 120582 which is of the order ofthe light cylinder in the central engine frame (120582 asymp 2120587119888Ω)whereΩ is the angular frequency of the central engine eithera spinning neutron star or black hole see [282] This polaritychange leads tomagnetic energy dissipation via reconnectionprocess It is assumed that the dissipation of magnetic energytakes place at a constant rate that is modeled by a fraction120598 of the Alfven speed As the details of the reconnectionprocess are uncertain the value of 120598 is highly uncertain Oftena constant value 120598 asymp 01 is assumed This implies that the(comoving) reconnection time is 1199051015840rec sim 120582

1015840120598V1015840119860 where V1015840

119860is

the (comoving) Alfven speed and 1205821015840 = Γ120582 Since the plasmais relativistic V1015840

119860sim 119888 and one finds that 1199051015840rec prop Γ In the lab

frame 119905rec = Γ1199051015840

rec prop Γ2

Assuming that a constant fraction of the dissipatedmagnetic energy is used in accelerating the jet the rate ofkinetic energy increase is therefore given by

119889119864119896

119889119903

prop

119889Γ

119889119903

sim

1119888119905rec

prop Γminus2 (22)

from which one immediately finds the scaling law Γ(119903) prop

11990313

The maximum Lorentz factor that can be achieved in thismechanism is calculated as follows First one writes the totalluminosity as 119871 = 119871

119896+ 119871119872

= (1205900 + 1)Γ01198882 where Γ0 is

the Lorentz factor of the flow at the Alfven radius Secondgeneralization of the Alfvenic velocity to relativistic speeds[283 284] reads

120574119860120573119860=

1198611015840

radic41205871198991198981199011198882=

119861Γ

radic41205871198991198981199011198882= radic120590 (23)

By definition of the Alfvenic radius the flow Lorentz factorat this radius is Γ0 = 120574

119860≃ radic1205900 (since at this radius the

flow is Poynting-flux dominated 1205900 ≫ 1) Thus the massejection rate is written as asymp 119871120590

320 119888

2 As the luminosityis assumed constant throughout the outflow the maximumLorentz factor is reached when 119871 sim 119871

119896≫ 119871119872 namely

119871 = Γmax1198882 Thus

Γmax asymp 120590320 (24)

In comparison to the photon-dominated outflow jetacceleration in the Poynting-flux dominated outflow modelis thus much more gradual The saturation radius is at119903119904= 1199030120590

30 asymp 1013512059032(120598Ω)

minus13 cm Similar calculations to that

presented above show the photospheric radius to be at radius[280]

119903ph = 6times 10111198713552

(120598Ω)253 120590

322

cm (25)

which is similar (for the values of parameters chosen) to thephotospheric radius obtained in the photon-dominated flow

Note that in this scenario the photosphere occurs while theflow is still accelerating

The model described above is clearly very simplistic Inparticular it assumes constant luminosity and constant rateof reconnection along the jet As such it is difficult to explainthe observed rapid variability in the framework of thismodelFurthermore one still faces the need to dissipate the kineticenergy in order to produce the observed 120574-rays Aswas shownby several authors [285ndash287] kinetic energy dissipation viashock waves is much less efficient in Poynting-flow domi-nated plasma relative to weakly magnetized plasma

Moreover even if this is the correct model in describing(even if only approximately) the magnetic energy dissipationrate it is not known what fraction of the dissipated magneticenergy is used in accelerating the jet (increasing the bulkLorentz factor) and what fraction is used in heating theparticles (increasing their random motion) Lacking cleartheoretical model it is often simply assumed that about halfof the dissipated energy is used in accelerating the jet theother half in heating the particles [288] Clearly all theseassumptions can be questioned Despite numerous efforts inrecent years in studying magnetic reconnection (eg [289ndash293]) this is still an open issue

Being aware of these limitations in recent years severalauthors have dropped the steady assumption and consideredmodels in which the acceleration of a magnetic outflowoccurs over a finite short duration [294ndash297] The basic ideais that variability in the central engine leads to the ejectionof magnetized plasma shells that expand due to internalmagnetic pressure gradient once they lose causal contact withthe source

One suggestion is that similar to the internal shockmodelthe shells collide at some radius 119903coll The collision distortthe ordered magnetic field lines entrained in the ejectaOnce reaching a critical point fast reconnection seeds occurwhich induce relativistic MHD turbulence in the interactionregions This model known as Internal-Collision-inducedMagnetic Reconnection and Turbulence (ICMART) [201]may be able to overcome the low efficiency difficulty of theclassical internal shock scenario

34 Particle Acceleration In order to produce the nonther-mal spectra observed one can in principle consider twomechanisms The first is emission of radiation via variousnonthermal processes such as synchrotron or ComptonThisis the traditional way which is widely considered in theliterature A second way which was discussed only recently isthe use of light aberration to modify the (naively expected)Planck spectrum emitted at the photosphere The potentialsand drawbacks of this second idea will be considered inSection 354 First let me consider the traditional way ofproducing the spectra via nonthermal radiative processes (aphotospheric emission cannot explain photons at the GeVrange and thus even if it does play a major role in producingthe observed spectra it is certainly not the only radiativemechanism)

The internal collisions magnetic reconnection or possi-bly other unknown mechanisms dissipate part of the outflow

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

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[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

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[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

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[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

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[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

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[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

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[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

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[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

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[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Superconductivity

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 Computational  Methods in Physics

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Soft MatterJournal of

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ThermodynamicsJournal of

18 Advances in Astronomy

kinetic energy (within the context of Poynting-flux domi-nated outflows it was suggested by Lyutikov and Blandford[200] and Lyutikov [298] that the magnetic energy dissipatedmay be converted directly into radiating particles withoutconversion to kinetic energy first) This dissipated energyin turn can be used to heat the particles (increase theirrandommotion) andor accelerate some fraction of them to anonthermal distribution Traditionally it is also assumed thatsome fraction of this dissipated energy is used in producing(or enhancing) magnetic fields Once accelerated the highenergy particles emit the nonthermal spectra

Themost widely discussedmechanism for acceleration ofparticles is the Fermi mechanism [299 300] which requiresparticles to cross back and forth a shock wave Thus thismechanism is naturally associated with internal shell col-lisions where shock waves are expected to form A basicexplanation of this mechanism can be found in the textbookby [301] For reviews see [302ndash305] In this process theaccelerated particle crosses the shock multiple times andin each crossing its energy increases by a (nearly) constantfractionΔ119864119864 sim 1This results in a power law distribution ofthe accelerated particles 119873(119864) prop 119864

minus119878 with power law index119878 asymp 20 minus 24 [306ndash310] Recent developments in particle-in-cell (PIC) simulations have allowed to model this processfrom first principles and study it in more detail [311ndash315] Ascan be seen in Figure 15 taken from [313] indeed a power lawtail above a low energyMaxwellian in the particle distributionis formed

The main drawback of the PIC simulations is that due tothe numerical complexity of the problem these simulationscan only cover a tiny fraction (sim10minus8) of the actual emittingregion in which energetic particles exist Thus these simu-lations can only serve as guidelines and the problem is stillfar from being fully resolved Regardless of the exact detailsit is clear that particle acceleration via the Fermi mechanismrequires the existence of shock waves and is thus directlyrelated to the internal dynamics of the gas and possibly to thegeneration of magnetic fields as mentioned above

The question of particle acceleration in magnetic recon-nection layers has also been extensively addressed in recentyears (see [289ndash293 316ndash331] for a partial list of works)The physics of acceleration is somewhat more complicatedthan in nonmagnetized outflows and may involve severaldifferentmechanismsThe basic picture is that the dissipationof the magnetic field occurs in sheets The first mechanismrelies on the realization that within these sheets there areregions of high electric fields particles can therefore beaccelerated directly by the strong electric fields A secondmechanism is based on instabilities within the sheets thatcreate ldquomagnetic islandsrdquo (plasmoids) that are moving closeto the Alfven speed (see Figure 16) Particles can therefore beaccelerated via Fermi mechanism by scattering between theplasmoids A thirdmechanism is based on converging plasmaflows towards the current sheets that provide another way ofparticle acceleration via first order Fermi process

In addition if the flow is Poynting-flux dominatedparticles may also be accelerated in shock waves howeverit was argued that Fermi-type acceleration in shock waves

106

104

102

100106

104

102

100

106

105

104

103

102

101

100

10minus1

(a)

(b)1 10 100 1000

1 10 100 1000

120574dN(120574)d120574

120574

Figure 15 Results of a particle in cell (PIC) simulation shows theparticle distribution downstream from the shock (black line) Thered line is a fit with a low energy Maxwellian and a high energypower law with a high energy exponential cutoff Subpanel (a) isthe fit with a sum of high and low temperature Maxwellians (redline) showing a deficit at intermediate energies subpanel (b) is thetime evolution of a particle spectrum in a downstream slice at threedifferent timesThe black dashed line shows a 120574minus24 power law Figuretaken from Spitkovsky [313]

that may develop in highly magnetized plasma may beinefficient [314 332] Thus while clearly addressing thequestion of particle acceleration in magnetized outflow is avery active research field the numerical limitations implythat theoretical understanding of this process and its details(eg what fraction of the reconnected energy is being usedin accelerating particles or the energy distribution of theaccelerated particles) is still very limited

Although the power law distribution of particles resultingfrom Fermi-type or perhaps magnetic-reconnection accel-eration is the most widely discussed we point out thatalternative models exist One such model involves particleacceleration by a strong electromagnetic potential whichcan exceed 1020 eV close to the jet core [333ndash335] Theaccelerated particles may produce a high energy cascade ofelectron-positron pairs Additional model involves stochasticacceleration of particles due to resonant interactions withplasma waves in the black hole magnetosphere [336]

Several authors have also considered the possibility thatparticles in fact have a relativistic quasi-Maxwellian distri-bution [337ndash340] Such a distribution with the requiredtemperature (sim1011-1012 K) may be generated if particles areroughly thermalized behind a relativistic strong shock wave(eg [341])While such amodel is consistent with several keyobservations it is difficult to explain the very high energy(GeV) emission without invoking very energetic particlesand therefore some type of particle acceleration mechanismmust take place as part of the kinetic energy dissipationprocess

35 Radiative Processes and the Production of the ObservedSpectra Following jet acceleration kinetic energy dissipa-tion (either via shock waves or via magnetic reconnection)

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

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GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

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 Computational  Methods in Physics

Journal of

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Soft MatterJournal of

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PhotonicsJournal of

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Journal of

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ThermodynamicsJournal of

Advances in Astronomy 19

6004002000

minus200minus400minus600

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

y 1(c120596

P)

x1(c120596P)

x1(c120596P)

0 500 1000 1500 2000 2500

Den

sity

Den

sity

120598 B120574minus

1

102

101

100

10minus1

102

101

10010minus1

102

101

10010minus1

101

100

10minus110minus2

(C)

0 1000 2000 3000 4000 5000 6000

100

0

minus100

100

0

minus100

100

0

minus100

(D)

(A)

(B)

(a)

0

2500

5000

p = 2

120574dNd120574

100

10minus2

10minus4

10minus6

100 101 102 103

120596Pt = 5200

120574dNd120574

120574

120574

100

10minus2

10minus4

10minus6100 101 102 103

120590 = 1120590 = 3120590 = 10

120590 = 30120590 = 50

Tim

e [120596Pminus1

]

(b)

Figure 16 Results of an electromagnetic particle in cell (PIC) simulation TRISTAN-MP show the structure of the reconnection layer (a) andthe accelerated particle distribution function (b) (a) Structure of the reconnection layer Shown are the particle densities (A) (B) magneticenergy fraction (C) and mean kinetic energy per particle (D) The plasmoids are clearly seen (b) Temporal evolution of particle energyspectrum The spectrum at late times resembles a power law with slope 119901 = 2 (dotted red line) and is clearly departed from a MaxwellianThe dependence of the spectrum on the magnetization is shown in the inset Figure is taken from Sironi and Spitkovsky [330]

and particle acceleration the final stage of energy conversionmust produce the observed spectra As the 120574-ray spectrais both very broad and nonthermal (does not resembleldquoPlanckrdquo) most efforts to date are focused on identifyingthe relevant radiative processes and physical conditions thatenable the production of the observed spectra The leadingradiativemodels initially discussed are synchrotron emissionaccompanied by synchrotron-self Compton at high energiesHowever as has already mentioned it was shown that thismodel is inconsistent with the data in particular the lowenergy spectral slopes

Various suggestions of ways to overcome this drawbackbymodifying some of the physical conditions andor physicalproperties of the plasma were proposed in the last decadeHowever a major revolution occurred with the realizationthat part of the spectra is thermal This led to new set ofmodels in which part of the emission originates from belowthe photosphere (the optically thick region) It should bestressed that only part of the spectrum but not all of it isassumed to originate from the photosphere Thus in thesemodels as well there is room for optically thin (synchrotronand IC) emission originating from a different locationFinally a fewmost recent works on light aberration show thatthe contribution of the photospheric emission may be muchbroader than previously thought

351 Optically Thin Model Synchrotron Synchrotron emis-sion is perhaps the most widely discussed model for explain-ing GRB prompt emission It has several advantages First ithas been extensively studied since the 1960s [342 343] andis the leading model for interpreting nonthermal emissionin AGNs XRBs and emission during the afterglow phase ofGRBs Second it is very simple it requires only two basicingredients namely energetic particles and a strongmagneticfield Both are believed to be produced in shock waves (or

magnetic reconnection phase) which tie it nicely to thegeneral ldquofireballrdquo (both ldquohotrdquo and ldquocoldrdquo) picture discussedabove Third it is broadband in nature (as opposed eg tothe ldquoPlanckrdquo spectrum) with a distinctive spectral peak thatcould be associated with the observed peak energy Fourthit provides a very efficient way of energy transfer as for thetypical parameters energetic electrons radiate nearly 100of their energy These properties made synchrotron emissionthe most widely discussed radiative model in the context ofGRB prompt emission (eg [79 80 213 214 218 344ndash349]for a very partial list)

Consider a source at redshift 119911which ismoving at velocity120573 equiv V119888 (corresponding Lorentz factor Γ = (1 minus 120573)

minus12) atangle 120579 with respect to the observer The emitted photonsare thus seen with a Doppler boost D = [Γ(1 minus 120573 cos 120579)]minus1Synchrotron emission from electrons having randomLorentzfactor 120574el in a magnetic field 119861 (all in the comoving frame) isobserved at a typical energy

120598ob119898=

32ℏ

119902119861

119898119890119888

1205742el

D

(1 + 119911)

= 175times 10minus191198611205742elD

(1 + 119911)erg

(26)

If this model is to explain the peak observed energy 120598ob asymp200 keV with typical Lorentz factor D ≃ Γ sim 100 (relevantfor on-axis observer) one obtains a condition on the typicalelectron Lorentz factor and magnetic field

1198611205742el ≃ 36times 1010 (1 + 119911

2) Γminus12 (

120598ob

200 keV)119866 (27)

Thus both strong magnetic field and very energetic electronsare required in interpreting the observed spectral peak as dueto synchrotron emission Such high values of the electrons

20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

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[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

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[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

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[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

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[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Superconductivity

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20 Advances in Astronomy

Lorentz factor are not excluded by any of the known modelsfor particle acceleration High values of the magnetic fieldsmay be present if the outflow is Poynting flux dominated Inthe photon-dominated outflow strongmagnetic fieldsmay begenerated in shockwaves via two stream (Weibel) instabilities[124 311 350ndash353]

One can therefore conclude that the synchrotronmodel iscapable of explaining the peak energyHowever one alarmingproblem is that the high values of both 119861 and 120574el requiredwhen expressed as fraction of available thermal energy (theparameters 120598

119890and 120598119861) aremuch higher than the (normalized)

values inferred from GRB afterglow measurements [354ndash357] This is of a concern since broadband GRB afterglowobservations are typically well fitted with the synchrotronmodel and the microphysics of particle acceleration andmagnetic field generation should be similar in both promptand afterglow environments (though the forward shockproducing the afterglow is initially highly relativistic whileshock waves produced during the internal collisions may bemildly relativistic at most)

Themain concern though is the low energy spectral slopeAs long as the electrons maintain their energy the expectedsynchrotron spectrum below the peak energy is 119865] prop ]13

(corresponding photon number 119873119864prop 119864minus23) (eg [118])

This is roughly consistent with the observed low energyspectral slope ⟨120572⟩ = minus1 (see Section 222)

However at these high energies and with such strongmagnetic field the radiating electrons rapidly cool by radi-ating their energy on a very short time scale

1199051015840

cool =119864

119875

=

120574el1198981198901198882

(43) 1198881205901198791205742el119906119861 (1 + 119884)

=

6120587119898119890119888

1205901198791198612120574el (1 + 119884)

(28)

Here 119864 = 120574el1198981198901198882 is the electronrsquos energy 119875 is the radiated

power 119906119861equiv 119861

28120587 is the energy density in themagnetic field

120590119879is Thomsonrsquos cross section and 119884 is Compton parameter

The factor (1 + 119884) is added to consider cooling via bothsynchrotron and Compton scattering

Using the values obtained in (27) one finds the (comov-ing) cooling time to be

1199051015840

cool = 60times 10minus131205743el (1+119884)minus1(

1 + 1199112

)

minus2

sdot Γ22 (

120598ob

200 keV)

minus2

s(29)

This time is to be compared with the comoving dynamicaltime 1199051015840dyn sim 119877Γ119888 If the cooling time is shorter than thedynamical time the resulting spectra below the peak are119865] prop ]minus12 (eg [358 359]) corresponding to 119873

119864prop

119864minus32 While values of the power law index smaller than

minus32 corresponding to shallow spectra can be obtainedby superposition of various emission sites steeper valuescannot be obtained Thus the observed low energy spectralslope of sim85 of the GRBs (see Figure 5) which show 120572

larger than this value (⟨120572⟩ = minus1) cannot be explained bysynchrotron emission model This is the ldquosynchrotron line ofdeathrdquo problem introduced above

The condition for 1199051015840cool ≳ 1199051015840

dyn can be written as

120574el ≳ 38times 1041198771314 (1+119884)13 (1 + 119911

2)

23

sdot Γminus12 (

120598ob

200 keV)

23

(30)

The value of the emission radius 119877 = 1014 cm is chosen asa representative value that enables variability over time scale120575119905

obsim 119877Γ

2119888 sim 0311987714Γ

minus22 s

Since 120574el represents the characteristic energy of the radi-ating electrons such high values of the typical Lorentz factor120574el are very challenging for theoretical modeling However amuch more severe problem is that in this model under theseconditions the energy content in the magnetic field must bevery low (see (27)) In order to explain the observed flux onemust therefore demand high energy content in the electronrsquoscomponent which is several orders ofmagnitude higher thanthat stored in the magnetic field [15 360 361] This in turnimplies that inverse Compton becomes significant producingsimTeV emission component that substantially increase thetotal energy budget As was shown by Kumar and McMahon[360] such a scenario can only be avoided if the emissionradius is119877 ≳ 1017 cm in which case it is impossible to explainthe rapid variability observed Thus the overall conclusionis that classical synchrotron emission as a leading radiativeprocess fails to explain the key properties of the promptemission of the vast majority of GRBs [85 362]

352 Suggested Modifications to the Classical SynchrotronScenario The basic synchrotron emission scenario thus failsto self-consistently explain both the energy of the spectralpeak and the low energy spectral slope In the past decadethere have been several suggestions of ways inwhich the basicpicture might be modified so that the modified synchrotronemission accompanied by inverse Compton scattering ofthe synchrotron photons (synchrotron-self Compton SSC)would be able to account for these key observations

The key problem is the fast cooling of the electronsnamely 119905cool lt 119905dyn However in order for the electrons torapidly cool they must be embedded in a strong magneticfield The spatial structure of the magnetic field is not clearat all Thus it was proposed by Persquoer and Zhang [363] that themagnetic field may decay on a relatively short length scaleand so the electrons would not be able to efficiently coolThisidea had gain interest recently [364 365] Its major drawbackis the need for high energy budget as only a small part of theenergy stored in the electrons is radiated

Another idea is that synchrotron self-absorption mayproduce steep low energy slope below the observed peak[366] However this requires unrealistically high magneticfield Typically the synchrotron self-absorption frequencyis expected at the IROptic band (eg [118 367]) Thussynchrotron self-absorption may be relevant in shaping

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Advances in Condensed Matter Physics

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International Journal of

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Superconductivity

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Statistical MechanicsInternational Journal of

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AstrophysicsJournal of

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Physics Research International

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 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

Advances in Astronomy 21

the spectrum at the X-rays only under very extreme condi-tions (eg [368])

Looking into a different parameter space region it wassuggested that the observed peak energy is not due to syn-chrotron emission but due to inverse-Compton scattering ofthe synchrotron photons which are emitted at much lowerenergies [369ndash371] In these models the steep low energyspectral slope can result from upscattering of synchrotronself-absorbed photons However a careful analysis of thisscenario (eg [15]) reveals requirements on the emissionradius 119877 ≳ 1016 cm and optical flux (associated withthe synchrotron seed photons) that are inconsistent withobservations Furthermore a second scattering would lead tosubstantial TeV flux resulting in an energy crisis [372 373]Thus this model as well is concluded as not being viable asthe leading radiativemodel during the GRB prompt emission[373]

If the energy density in the photon field is much greaterthan in the magnetic field then electron cooling by inverseCompton scattering the low energy photons dominatesovercooling by synchrotron radiation The most energeticelectrons cool less efficiently due to the Klein-Nishina (KN)decrease in the scattering cross sectionThus in this parame-ter space where KN effect is important steeper low energyspectral slopes can be obtained [372 374 375] Howevereven under the most extreme conditions the steepest slopethat can be obtained is no harder than 119865] sim ]0 [374 376]corresponding to 119873

119864prop 119864minus1 which can explain at most

sim50 of the low energy spectral slopes observed Moreoververy high values of the electronrsquos Lorentz factor 120574el ≳ 106are assumedwhich challenge theoreticalmodels as discussedabove

A different proposition was that the heating of the elec-tronsmay be slow namely the electronsmay be continuouslyheated while radiating their energy as synchrotron photonsThis way the rapid electrons cooling is avoided and ashallower spectra can be obtained [360 377ndash380] Whilethere is no known mechanism that could continuously heatthe electrons as they cross the shock wave and are advecteddownstream in the classical internal collision scenario it wasproposed that slow heatingmay result fromMHD turbulencedown stream of the shock front [380] Thus this may be aninteresting alternative though currently there are still largegaps in the physics involved in the slow heating process

Several authors considered the possibility of synchrotronemission from nonisotropic electron distribution [366 381]Alternatively the magnetic field may vary on such a shortscale that relativistic electrons transverse deflection is muchsmaller than the beaming angle [382]This results in a ldquojitterrdquoradiation with different spectral properties than classicalsynchrotron

A different suggestion is emission by the hadrons (pro-tons)The key idea is that whatevermechanism that is capableof accelerating electrons to high energies should accelerateprotons as well in fact the fact that high energy cosmic raysare observed necessitate the existence of such a mechanismalthough its details in the context of GRBs are unknownMany authors have considered possible contribution ofenergetic protons to the observed spectra (eg [383ndash389])

Energetic proton contribution to the spectrum is both viadirect synchrotron emission and also indirectly by photopionproduction or photopair production

Clearly proton acceleration to high energies would implythat GRBs are potentially strong source of both high energycosmic rays and energetic neutrinos [390ndash393] On the otherhand the main drawback of this suggestion is that protonsare much less efficient radiators than electrons (as the ratioof proton to electron cross section for synchrotron emissionis sim (119898

119890119898119901)2) Thus in order to produce the observed

luminosity in 120574-rays the energy content of the protons mustbe very high with proton luminosity of sim1055-1056 erg sminus1This is at least 3 orders of magnitude higher than therequirement for leptonic models

353 Photospheric Emission As discussed above photo-spheric (thermal) emission is an inherent part of both theldquohotrdquo and ldquocoldrdquo (magnetized) versions of the fireball modelThus it is not surprising that the very early models of cosmo-logical GRBs considered photospheric emission as a leadingradiative mechanism [77 78 184 197] However followingthe observational evidence of a nonthermal emission andlacking clear evidence for a thermal component this idea wasabandoned for over a decade

Renewed interest in this idea began in the early 2000swith the realization that the synchrotron model even afterbeing modified cannot explain the observed spectra Thusseveral authors considered addition of thermal photons tothe overall nonthermal spectra being either dominant [394395] or subdominant [239 240 396] Note that as neitherthe internal collision or the magnetic reconnection modelsprovide clear indication of the location and the amount ofdissipated kinetic energy that is later converted into nonther-mal radiation it is impossible to determine the expected ratioof thermal to nonthermal photons from first principles inthe framework of these models Lacking clear observationalevidence it was therefore thought that 119903ph ≫ 119903

119904 in which

case adiabatic losses lead to strong suppression of the thermalluminosity and temperature (see (18) and (19))

However as was pointed out by Persquoer and Waxman[397] in the scenario where 119903ph ≫ 119903

119904it is possible that

substantial fraction of kinetic energy dissipation occursbelow the photosphere (eg in the internal collision scenarioif 119903coll lt 119903ph) In this case the radiated (nonthermal)photons that are emitted as a result of the dissipation processcannot directly escape but are advected with the flow untilthey escape at the photosphere This triggers several eventsFirst multiple Compton scattering substantially modifiesthe optically thin (synchrotron) spectra presumably emittedinitially by the heated electrons Second the electrons inthe plasma rapidly cool mainly by IC scattering Howeverthey quickly reach a ldquoquasisteady staterdquo and their distribu-tion becomes quasi-Maxwellian irrespective of their initial(accelerated) distribution The temperature of the electronsis determined by balance between heating both externaland by direct Compton scattering energetic photons andcooling (adiabatic and radiative) [398] The photon fieldis then modified by scattering from this quasi-Maxwellian

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

22 Advances in Astronomy

10minus6

10minus7

10minus8

10minus9

10minus10

10minus11

10minus12

10minus13

10minus14101 102 103 104 105 106 107 108 109 1010 1011

Obs energy (eV)

120591120574e = 1000

120591120574e = 100

120591120574e = 10

120591120574e = 1

120591120574e = 01

120591120574e = 001

F

Flux

(e

rgcm

minus2sminus

1 )

Figure 17 Time averaged broadband spectra expected followingkinetic energy dissipation at various optical depths For low opticaldepth the two low energy bumps are due to synchrotron emissionand the original thermal component and the high energy bumpsare due to inverse Compton phenomenon At high optical depth120591 ge 100 a Wien peak is formed at sim10 keV and is blue-shifted tothe MeV range by the bulk Lorentz factor ≃100 expected in GRBsIn the intermediate regime 01 lt 120591 lt 100 a flat energy spectrumabove the thermal peak is obtained bymultiple Compton scatteringFigure is taken from Persquoer et al [399]

distribution of electrons The overall result is a regulation ofthe spectral peak at sim1MeV (for dissipation that takes place atmoderate optical depth 120591 sim a fewmdashfew tens) and low energyspectral slopes consistent with observations [397]

The addition of the thermal photons that originate fromthe initial explosion (this term is more pronounced if 119903ph ≳

119903119904) significantly enhances these effects [399] The thermal

photons serve as seed photons for IC scattering resultingin rapid cooling of the nonthermal electrons that are heatedin the subphotospheric energy dissipation event As therapid IC cooling leads to a quasisteady state distribution ofthe electrons the outcome is a ldquotwo-temperature plasmardquowith electron temperature higher than the thermal photontemperature 119879el gt 119879ph An important result of this modelis that the electron temperature is highly regulated and isvery weakly sensitive to themodel uncertainties see [398] fordetails If the dissipation occurs at intermediate optical depth120591 sim a fewmdashfew tens the emerging spectrum has a nearlyldquotop hatrdquo shape (see Figure 17) Below 119879ph the spectrumis steep similar to the Rayleigh-Jeans part of the thermalspectrum in between119879ph and119879el a nearly flat energy spectra]119891] prop ]0 (corresponding 119873

119864prop 119864minus2) is obtained resulting

frommultiple Compton scattering and an exponential cutoffis expected at higher energies

Interestingly the spectral slope obtained in the interme-diate regime is similar to the obtained high energy spectralslope ⟨120573⟩ sim minus2 (see discussion in Section 222 and Figure 5)Thus a simple interpretation is to associate the observed 119864pkwith119879ph However this is likely a too simplistic interpretation

from the following reasons First the predicted low energyspectral slopes being (modified) thermal are typically harderthan the observed [104] Second in GRB110721A the peakenergy is at asymp15MeV at early times [98 99] which is toohigh to be accounted for by 119879ph [400 401] Moreover recentanalysis of Fermi data shows a thermal peak at lower energiesthan 119864pk (see eg Figure 7) which is consistent with theinterpretation of the thermal peak being associated with 119879phThe key result of this model that 119879ph lt 119879el is consistent withthe observational result of 119864peakth lt 119864pk which is applicableto all GRBs in which thermal emission was identified so farThis model thus suggests that 119864pk may be associated with 119879elthough it does not exclude synchrotron origin for 119864pk seefurther discussion below

If the optical depth inwhich the kinetic energy dissipationtakes place is 120591 ≳ 100 the resulting spectra are closeto thermal while if 120591 ≲ a few the result is a complexspectra with synchrotron peak thermal peak and at leasttwo peaks resulting from IC scattering (see Figure 17) Belowthe thermal peak the main contribution is from synchrotronphotons that are emitted by the electrons at the quasi steadydistribution Above the thermal peak multiple IC scatteringis the main emission process resulting in nearly flat energyspectra Thus this model naturally predicts different spectralslopes below and above the thermal peak

Interestingly the key results of this model do not changeif one considers highly magnetized plasma [279 402ndash406]Indeed as this model of subphotospheric energy dissipationis capable of capturing the key observed features of theprompt emission it attracted a lot of attention in recent years(eg [104 236 401 407ndash422])

It should be noted that the above analysis holds for asingle dissipation episode In explaining the complex GRBlight curve multiple such episodes (eg internal collisions)are expected Thus a variety of observed spectra which aresuperposition of the different spectra that are obtained bydissipation at different optical depth are expected [423]

In spite if this success this model still suffers two maindrawbacks The first one already discussed is the need toexplain low energy spectral slopes that are not as hard as theRayleigh-Jeans part of a Planck spectra Further this modelneeds to explain the high peak energy (gtMeV) observed insome bursts in a self-consistent way A second drawbackis the inability of the subphotospheric dissipation model toexplain the very high energy (GeV) emission seen Such highenergy photons must originate from some dissipation abovethe photosphere

There are two solutions to these problems The first isgeometric in nature and takes into account the nonsphericalnature of GRB jets to explain how low energy spectral slopesare modified This will be discussed below The second is therealization that the photospheric emission must be accom-panied by at least another one dissipation process that takesplace above the photosphere This conclusion however isalignedwith both observations of different temporal behaviorof the high energy component (see Section 225) as well aswith the basic idea of multiple dissipation episodes inherentto both the ldquointernal collisionrdquo model and to the magneticreconnection model

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

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[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

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[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

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[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

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[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

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[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

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[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

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[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

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28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

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[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

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[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

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[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Advances in Condensed Matter Physics

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Superconductivity

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Statistical MechanicsInternational Journal of

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AstrophysicsJournal of

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Physics Research International

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Solid State PhysicsJournal of

 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

Advances in Astronomy 23

Indeed in the one case in which detailed modeling wasdone by considering two emission zones (photosphere andexternal one) very good fits to the data of GRB090902B wereobtained [229] This fits were done with a fully physicallymotivated model which enables determining the physicalconditions at both emission zones [229]This is demonstratedin Figure 18

354 Geometrical Broadening As was already discussed inSection 325 the definition of the photosphere as the lastscattering surface must be modified to incorporate the factthat photons have finite probability of being scattered at everylocation in space where particles existThis led to the conceptof ldquovague photosphererdquo (see Figure 14) The observationalconsequences of this effect were studied by several authors[236 241 242 244 424ndash426] In spherical explosion casethe effect of the vague photosphere is not large it somewhatmodifies the Rayleigh-Jeans part of the spectrum to read119865] prop ]32 [242] However for nonspherical explosion theeffect becomes dramatic

While the exact geometry of GRB jets namely Γ(119903 120579 120601)are unknown numerical simulations of jets propagatingthrough the stellar core (eg [427]) suggest a jet profile ofthe form Γ(120579) sim Γ0(1 + (120579120579119895)

2119901) at least for nonmagnetized

outflows Such a jet profile thus assumes a constant Lorentzfactor Γ sim Γ0 for 120579 ≲ 120579

119895(the ldquojet corerdquo or inner jet)

and decaying Lorentz factor at larger angles Γ(120579) prop 120579minus119901

(outer jet or jet sheath) As the Lorentz factor is Γ prop 119871

(Section 323) such a profile can result from excess of massload close to the jet edge by mass collected from the star( = (120579)) or alternatively by angle dependent luminosity

The scenario of = (120579) was considered by Lundmanet al [244] While photospheric emission from the innerparts of the jet results in mild modification to the black bodyspectrum photons emitted from the outer jetrsquos photospheredominate the spectra at low energies (see Figure 19) Fornarrow jets (120579

119895Γ0 ≲ few) this leads to flat low energy spectra

119889119873119889119864 prop 119864minus1 which is independent on the viewing angle

and very weakly dependent on the exact jet profileThis resultthus both suggests the possibility that the low energy slopesare in fact part of the photospheric emission and in additioncan be used to infer the jet geometry

A second aspect of the model is that the photosphericemission can be observed to be highly polarized with up toasymp40 polarization [429 430] While IC scattering produceshighly polarized light in spherical models the polarizationfrom different viewing angles cancels However this cancel-lation is incomplete in jet-like models (observed off-axis)While the observed flux by an observer off the jet axis (thatcan see highly polarized light) is reduced it is still highenough to be detected [429]

A third unique aspect that results from jet geometry(rather than spherical explosion) is photon energy gain byFermi-like process As photons are scattered back and forthbetween the jet core and the sheath on the average they gainenergy This leads to a high energy power law tail (above thethermal peak) [244 431]This againmay serve as a new tool instudying jet geometry though the importance of this effect in

10minus6

10minus7

10minus8

10minus5

104102 108106 10121010

Obs energy (eV)

F

Obs

flux

(e

rg cm

minus2

sminus1 )

Figure 18 Spectral decomposition of GRB090902B (taken at timeinterval (119888) 96ndash130 seconds after the GBM trigger) enables clearidentification of the physical origin of the emissionThe dash-dotted(red) curve shows the spectrum that would have been obtained ifsynchrotron radiation was the only source of emission The dashed(green) curve shows the resulting spectrum from synchrotron andSSC and the solid (blue) curve shows the spectrum with the fullradiative ingredients (synchrotron SSC the simMeV thermal peakand Comptonization of the thermal photons) Numerical fits aredone using the radiative code developed by Persquoer andWaxman [428]Figure is taken from Persquoer et al [229]

determining the high energy spectra of GRBs is still not fullyclear (Lundman et al in prep)

355 A Few Implications of the Photospheric Term A greatadvantage of the photospheric emission in its relative sim-plicity By definition the photosphere is the innermost regionfrom which electromagnetic signal can reach the observerThus the properties of the emission site are much moreconstrained relative for example to synchrotron emission(whose emission radius magnetic field strength and particledistribution are not known)

In fact in the framework of the ldquohotrdquo fireball modelthe (1-d) photospheric radius is a function of only twoparameters the luminosity (which can be measured once thedistance is known) and the Lorentz factor (see (17)) Thephotospheric radius is related to the observed temperatureand flux via 119903phΓ prop (119865

obbb 120590119879

ob4)14 where 120590 is Stefanrsquos

constant and the extra factor of Γminus1 is due to light aberrationSince 119903ph prop 119871Γ

minus3 measurements of the temperature andflux in bursts with known redshift enables an independentmeasurement of Γ the Lorentz factor at the photosphere[432] This in turn can be used to determine the fulldynamical properties of the outflow

One interesting result is that by using this method itis found that 1199030 the size of the jet base is sim1085 cm two-three orders of magnitude above the Schwarzschild radius[99 101 432 433] Interestingly this result is aligned withrecent constraints found by Vurm et al [416] that showedthat the conditions for full thermalization takes place only if

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

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[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

24 Advances in Astronomy

101

100 Inner jetOuter jetEnvelope

10minus310minus410minus510minus610minus710minus810minus9 10minus2 10minus1

10minus3

10minus4

10minus5

10minus2

10minus1

101100

Emec2

Fob E

(erg

cmminus2

sminus1

ergminus

1 )

EenvEe ED

Ej Epeak

(a)

103

102

101

100

Γ(120579)

Γ = Γ0

Γ prop 120579minusp

Γ = Γmin

120579 = 120579j 120579 = 1205790

Inner jet Outer jet Envelope

12057910minus3 10minus2 10minus1 100

(b)

Figure 19 (a) The expected (observed) spectrum from a relativistic optically thick outflow The resulting spectra does not resemble thenaively expected ldquoPlanckrdquo spectrum Separate integration of the contributions from the inner jet (where Γ asymp Γ0) outer jet (where Γ dropswith angle) and envelope is shown with dashed dot dashed and dotted lines respectively (b) The assumed jet profile Figure taken fromLundman et al [244]

dissipation takes place at intermediate radii sim1010 cm wherethe outflow Lorentz factor is mild Γ sim 10 Furthermore thisradius of sim1085 cm is a robust radius where jet collimationshock is observed in numerical simulations [427 434] Theseresults thus point towards a new understanding of the earlyphases of jet dynamics

A second interesting implication is an indirect way ofconstraining the magnetization of the outflow It was shownby Zhang and Meszaros [435] Daigne and Mochkovitch[395] and Zhang and Persquoer [436] that for similar parametersthe photospheric contribution in highly magnetized outflowsis suppressed Lack of pronounced thermal component cantherefore be used to obtain a lower value on the magnetiza-tion parameter 120590 [436] Furthermore it was recently shown[405] that in fact in the framework of standard magneticreconnection model conditions for full thermalization donot exist in the entire region below the photosphere Asa result the produced photons are upscattered and theresulting peak of theWien distribution formed is at ≳10MeVThis again leads to the conclusion that identification ofthermal component at energies of ≲100 keV must imply thatthe outflow cannot be highly magnetized

4 Summary and Conclusion

We are currently in the middle of a very exciting epochin the study of GRB prompt emission Being very shortrandom and nonrepetitive study of the prompt emission isnotoriously difficult The fact that no two GRBs are similarmakes it extremely difficult to draw firm conclusions that arevalid for all GRBs Nonetheless following the launch of Swiftand Fermi ample observational and theoretical efforts havebeen put in understanding the elusive nature of these complexevents I think that it is fair to say that we are finally close tounderstanding the essence of it

To my opinion there are two parts to the revolutionthat took place in the last few years The first is the raiseof the time-dependent spectral analysis which enables adistinction between different spectral components that showdifferent temporal evolution A particularly good example isthe temporal behavior of the high energy (GeV) part of thespectrum that is lagging behind lower energy photons Thistemporal distinction enables a separate study of each com-ponent and points towards more than a single emission zoneThis distinction in fact is alignedwith the initial assumptionsof the ldquofireballrdquo model in which internal collisions (or severalepisodes of magnetic energy dissipation) lead to multipleemission zones

The second part of the revolution is associated with theidentification of a thermal component on top of the nonther-mal spectra For many years until today the standard fittingofGRB spectrawere and still are carried using amathematicalfunction namely the ldquoBandrdquo model Being mathematical innature this model does not have any ldquopreferredrdquo physicalscenario but its results can be interpreted in more than oneway As a result it is difficult to obtain a theoretical insightusing these fits As was pointed out over 15 years ago basicradiative models such as synchrotron fail to provide a validinterpretation to the obtained results Moreover while a greatadvantage of this model is its simplicity here lies also itsmost severe limitation being very simply it is not able toaccount for many spectral and temporal details which arelikely crucial in understanding the underlying physics ofGRBs

It was only in recent years with the abandoning ofthe ldquoBandrdquo model as a sole model for fitting GRB promptemission data that rapid progress was enabled The intro-duction of thermal emission component played a key role inthis revolution First it provides a strongly physically moti-vated explanation to at least part of the spectrum Second

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Biophysics

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ThermodynamicsJournal of

Advances in Astronomy 25

the values of the parameters describing the nonthermal partof the spectra are different than the values derived withoutthe addition of a thermal component this makes it easierto provide a physical interpretation to the nonthermal partThird the observed well defined temporal behavior openeda new window into exploring the temporal evolution of thespectra These observational realizations triggered a wealthof theoretical ideas aimed at explaining both the observedspectral and temporal behaviors

Currently there is still no single theoretical model thatis accepted by the majority of the community This is due tothe fact that although it is clear that synchrotron emissionfrom optically thin regions cannot account for the vastmajority of GRBs pure thermal component is only rarelyobserved Furthermore clearly the very high energy (GeVband) emission has a nonthermal origin and therefore evenif thermal component does play an important role theremust be additional processes contributing to the high energypart Moreover while thermal photons are observed in someGRBs there are others in which there is no evidence for sucha component Thus whatever theoretical idea may be usedto explain the data it must be able to explain the diversityobserved

At present epoch there are three leading suggestionsfor explaining the variety of the data The first is that thevariety seen is due to different in magnetization It is indeeda very appealing idea if it can be proved that the variety ofobserved spectra depends only on a single parameter Thesecond type of models consider the different jet geometriesand the different observing angles relative to the jet axis Thisis a novel approach never taken before and as such thereis ample of room for continuing research in this directionThe third type of models considers subphotospheric energydissipation as a way of broadening the ldquoPlanckrdquo spectra Theobserved spectra in these models thus mainly depend on thedetails of the dissipation process and in particular the opticaldepth in which it takes place

All of these models hold great promise as they enable notonly to identify directly the key ingredients that shape theobserved spectra but also to use observations to directly inferphysical properties These include the jet dynamics Lorentzfactor geometry (Γ as a function of 119903 120579 and maybe also 120601)and even the magnetization Knowledge of these quantitiesthus directly reflects on answering basic questions of greatinterest to astronomy such as jet launching composition andcollimation

Thus to conclude my view is that we are in the middle ofthe ldquoprompt emission revolutionrdquo It is too early to claim thatwe fully understand the prompt emission indeed we havereached no consensus yet about many of the key propertiesas is reflected by the large number of different ideas Howeverwe understand various key properties of the prompt emissionin a completely different way than only 5ndash10 years ago ThusI believe that another 5ndash10 years from now there is a goodchance that we could get to a conclusive idea about thenature of the prompt emission and would be able to useit as a great tool in studying many other important issuessuch as stellar evolution gravitational waves and cosmicrays

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The author would like to thank Felix Ryde for numeroususeful discussions

References

[1] E Waxman ldquoGamma-ray bursts the underlying modelrdquo inSupernovae and Gamma-Ray Bursters KWeiler Ed vol 598 ofLectureNotes in Physics pp 393ndash418 Springer Berlin Germany2003

[2] T Piran ldquoThe physics of gamma-ray burstsrdquo Reviews of ModernPhysics vol 76 no 4 pp 1143ndash1210 2004

[3] B Zhang and P Meszaros ldquoGamma-ray bursts progressproblems amp prospectsrdquo International Journal of Modern PhysicsA vol 19 no 15 pp 2385ndash2472 2004

[4] PMeszaros ldquoGamma-ray burstsrdquoReports on Progress in Physicsvol 69 no 8 pp 2259ndash2321 2006

[5] E Nakar ldquoShort-hard gamma-ray burstsrdquo Physics Reports vol442 no 1ndash6 pp 166ndash236 2007

[6] B Zhang ldquoGamma-ray bursts in the swift erardquo Chinese Journalof Astronomy and Astrophysics vol 7 no 1 pp 1ndash50 2007

[7] Y-Z Fan and T Piran ldquoHigh-energy 120574-ray emission fromgamma-ray burstsmdashbefore GLASTrdquo Frontiers of Physics inChina vol 3 no 3 pp 306ndash330 2008

[8] N Gehrels E Ramirez-Ruiz andD B Fox ldquoGamma-ray burstsin the swift erardquo Annual Review of Astronomy and Astrophysicsvol 47 pp 567ndash617 2009

[9] J-L Atteia and M Boer ldquoObserving the prompt emission ofGRBsrdquo Comptes Rendus Physique vol 12 no 3 pp 255ndash2662011

[10] N Gehrels and P Meszaros ldquoGamma-ray burstsrdquo Science vol337 no 6097 pp 932ndash936 2012

[11] N Bucciantini ldquoMagnetars and gamma ray burstsrdquo in Proceed-ings of the IAU Symposium Death of Massive Stars Supernovaeand Gamma-Ray Bursts vol 279 pp 289ndash296 2012

[12] N Gehrels and S Razzaque ldquoGamma-ray bursts in the swift-Fermi erardquo Frontiers of Physics vol 8 no 6 pp 661ndash678 2013

[13] F Daigne ldquoGRB prompt emission and the physics of ultra-relativistic outflowsrdquo in Gamma-Ray Bursts 15 Years of GRBAfterglows A J Castro-Tirado J Gorosabel and IH Park Edsvol 61 of Park EAS Publications Series pp 185ndash191 EAS 2013

[14] B Zhang ldquoGamma-ray burst prompt emissionrdquo InternationalJournal of Modern Physics D vol 23 no 2 Article ID 143000218 pages 2014

[15] P Kumar and B Zhang ldquoThe physics of gamma-ray bursts andrelativistic jetsrdquo Physics Reports vol 561 pp 1ndash109 2015

[16] E Berger ldquoShort-duration gamma-ray burstsrdquo Annual Reviewof Astronomy and Astrophysics vol 52 no 1 pp 43ndash105 2014

[17] PMeszaros andM J Rees ldquoGamma-ray burstsrdquo inGeneral Rel-ativity andGravitation ACentennial Perspective A Ashtekar BBerger J Isenberg and M A H MacCallum Eds CambridgeUniversity Press Cambridge UK 2014

[18] B Gendre G Stratta J L Atteia et al ldquoThe ultra-long gamma-ray burst 111209A the collapse of a blue supergiantrdquo TheAstrophysical Journal vol 766 no 1 article 30 2013

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

26 Advances in Astronomy

[19] C Kouveliotou C A Meegan G J Fishman et al ldquoIdentifi-cation of two classes of gamma-ray burstsrdquo The AstrophysicalJournal vol 413 no 2 pp 101ndash104 1993

[20] W S Paciesas C AMeegan G N Pendleton et al ldquoThe fourthBATSE gamma-ray burst catalog (revised)rdquo The AstrophysicalJournal vol 122 no 2 pp 465ndash495 1999

[21] W S Paciesas C A Meegan A von Kienlin et al ldquoTheFermi GBM gamma-ray burst catalog the first two yearsrdquo TheAstrophysical Journal Supplement Series vol 199 no 1 article18 2012

[22] Y Qin E-W Liang Y-F Liang et al ldquoA comprehensive analysisof fermi gamma-ray burst data III energy-dependent T

90

distributions of GBM GRBs and instrumental selection effecton duration classificationrdquo The Astrophysical Journal vol 763no 1 article 15 2013

[23] A von Kienlin C A Meegan W S Paciesas et al ldquoThe secondFermi GBM gamma-ray burst catalog the first four yearsrdquoTheAstrophysical Journal Supplement Series vol 211 no 1 article 132014

[24] T Sakamoto S D Barthelmy W H Baumgartner et al ldquoThesecond Swift Burst Alert Telescope gamma-ray burst catalogrdquoThe Astrophysical Journal Supplement Series vol 195 no 1article 2 2011

[25] Z Bosnjak D Gotz L Bouchet S Schanne and B CordierldquoThe spectral catalogue of INTEGRAL gamma-ray burstsresults of the joint IBISSPI spectral analysisrdquo Astronomy ampAstrophysics vol 561 article 25 2014

[26] T J Galama P M Vreeswijk J van Paradijs et al ldquoAn unusualsupernova in the error box of the 120574-ray burst of 25 April 1998rdquoNature vol 395 no 6703 pp 670ndash672 1998

[27] J Hjorth J Sollerman P Moslashller et al ldquoA very energeticsupernova associated with the 120574-ray burst of 29 March 2003rdquoNature vol 423 no 6942 pp 847ndash850 2003

[28] K Z Stanek T Matheson P M Garnavich et al ldquoSpectro-scopic discovery of the supernova 2003dh associated with GRB030329rdquoTheAstrophysical Journal Letters vol 591 no 1 pp L17ndashL20 2003

[29] S Campana V Mangano A J Blustin et al ldquoThe associationof GRB 060218 with a supernova and the evolution of the shockwaverdquo Nature vol 442 no 7106 pp 1008ndash1010 2006

[30] E Pian P A Mazzali N Masetti et al ldquoAn optical supernovaassociated with the X-ray flash XRF 060218rdquo Nature vol 442no 7106 pp 1011ndash1013 2006

[31] B E Cobb J S Bloom D A Perley A N Morgan S B Cenkoand A V Filippenko ldquoDiscovery of SN 2009nz associated withGRB 091127rdquo The Astrophysical Journal Letters vol 718 no 2pp L150ndashL155 2010

[32] R L C Starling K Wiersema A J Levan et al ldquoDiscoveryof the nearby long soft GRB100316D with an associated super-novardquo Monthly Notices of the Royal Astronomical Society vol411 no 4 pp 2792ndash2803 2011

[33] D A Kann S Klose B Zhang et al ldquoThe afterglows of swift-era gamma-ray bursts II Type I GRB versus type II GRB opticalafterglowsrdquoAstrophysical Journal vol 734 no 2 article 96 2011

[34] N Gehrels C L Sarazin P T OrsquoBrien et al ldquoA short 120574-ray burstapparently associated with an elliptical galaxy at redshift z =0225rdquo Nature vol 437 no 7060 pp 851ndash854 2005

[35] D B Fox D A Frail P A Price et al ldquoThe afterglow of GRB050709 and the nature of the short-hard 120574-ray burstsrdquo Naturevol 437 no 7060 pp 845ndash850 2005

[36] J S Villasenor D Q Lamb G R Ricker et al ldquoDiscovery ofthe short 120574-ray burst GRB 050709rdquo Nature vol 437 no 7060pp 855ndash858 2005

[37] S D Barthelmy G Chincarini D N Burrows et al ldquoAn originfor short 120574-ray bursts unassociated with current star formationrdquoNature vol 438 no 7070 pp 994ndash996 2005

[38] J Hjorth J Sollerman J Gorosabel et al ldquoGRB 050509B con-straints on short gamma-ray burst modelsrdquo The AstrophysicalJournal Letters vol 630 no 2 pp L117ndashL120 2005

[39] J S Bloom J X Prochaska D Pooley et al ldquoClosing in on ashort-hard burst progenitor constraints from early-time opticalimaging and spectroscopy of a possible host galaxy of GRB050509brdquo Astrophysical Journal Letters vol 638 no 1 pp 354ndash368 2006

[40] E Troja A R King P T OrsquoBrien N Lyons and GCusumano ldquoDifferent progenitors of short hard gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 385 no 1 pp L10ndashL14 2008

[41] W Fong and E Berger ldquoThe locations of short gamma-raybursts as evidence for compact object binary progenitorsrdquoAstrophysical Journal vol 776 no 1 article 18 2013

[42] B Zhang B-B Zhang E N-W Liang N Gehrels D NBurrows and P Meszaros ldquoMaking a short gamma-ray burstfrom a long one implications for the nature of GRB 060614rdquoThe Astrophysical Journal vol 655 no 1 pp L25ndashL28 2007

[43] M Nysewander A S Fruchter and A PersquoEr ldquoA comparison ofthe afterglows of short- and long-duration gamma-ray burstsrdquoThe Astrophysical Journal vol 701 no 1 pp 824ndash836 2009

[44] B Zhang B-B Zhang F J Virgili et al ldquoDiscerning the physicalorigins of cosmological gamma-ray bursts based on multipleobservational criteria the cases of 119911 = 67GRB 080913 119911 =

82GRB 090423 and some shorthard GRBsrdquoTheAstrophysicalJournal vol 703 no 2 pp 1696ndash1724 2009

[45] F J Virgili B Zhang POrsquoBrien andE Troja ldquoAre all short-hardgamma-ray bursts produced from mergers of compact stellarobjectsrdquoThe Astrophysical Journal vol 727 no 2 2011

[46] J P Norris N Gehrels and J D Scargle ldquoHeterogeneity in shortgamma-ray burstsrdquo The Astrophysical Journal vol 735 no 1article 23 2011

[47] E Berger ldquoThe environments of short-duration gamma-raybursts and implications for their progenitorsrdquo New AstronomyReviews vol 55 no 1-2 pp 1ndash22 2011

[48] O Bromberg E Nakar T Piran and R Sari ldquoShort versus longand collapsars versus non-collapsars a quantitative classifica-tion of gamma-ray burstsrdquoAstrophysical Journal vol 764 no 2article 179 2013

[49] W Fong E Berger R Chornock et al ldquoDemographics ofthe galaxies hosting short-duration gamma-ray burstsrdquo TheAstrophysical Journal vol 769 no 1 article 56 2013

[50] S Mukherjee E D Feigelson G J Babu F Murtagh CFralev and A Raftery ldquoThree types of gamma-ray burstsrdquo TheAstrophysical Journal vol 508 no 1 pp 314ndash327 1998

[51] I Horvath ldquoA third class of gamma-ray burstsrdquoThe Astrophys-ical Journal vol 508 no 2 pp 757ndash759 1998

[52] I Horvath L G Balazs Z Bagoly F Ryde and A Meszaros ldquoAnew definition of the intermediate group of gamma-ray burstsrdquoAstronomy and Astrophysics vol 447 no 1 pp 23ndash30 2006

[53] P Veres Z Bagoly I Horvath AMeszaros and L G Balazs ldquoAdistinct peak-flux distribution of the third class of gamma-raybursts a possible signature of X-ray flashesrdquoThe AstrophysicalJournal vol 725 no 2 pp 1955ndash1964 2010

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

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ThermodynamicsJournal of

Advances in Astronomy 27

[54] J Hakkila T W Giblin R J Roiger D J Haglin W S Paciesasand C A Meegan ldquoHow sample completeness affects gamma-ray burst classificationrdquo Astrophysical Journal Letters vol 582no 1 pp 320ndash329 2003

[55] J P Norris J T Bonnell D Kazanas J D Scarole J Hakkilaand TW Giblin ldquoLong-lag wide-pulse gamma-ray burstsrdquoTheAstrophysical Journal vol 627 no 1 pp 324ndash345 2005

[56] EW Liang B Zhang P T OrsquoBrien et al ldquoTesting the curvatureeffect and internal origin of gamma-ray burst prompt emissionsand X-ray flares with Swift datardquo Astrophysical Journal Lettersvol 646 no 1 pp 351ndash357 2006

[57] A A Abdo M Ackermann M Arimoto et al ldquoFermi observa-tions of high-energy gamma-ray emission fromGRB 080916CrdquoScience vol 323 no 5922 pp 1688ndash1693 2009

[58] T W Giblin V Connaughton J van Paradijs et al ldquoExtendedpower-law decays in batse gamma-ray bursts signatures ofexternal shocksrdquo Astrophysical Journal Letters vol 570 no 2pp 573ndash587 2002

[59] L Nicastro J J M Inrsquot Zand L Amati et al ldquoMultiwavelengthstudy of the very long GRB 020410rdquo Astronomy and Astro-physics vol 427 no 2 pp 445ndash452 2004

[60] F J Virgili C G Mundell V PalrsquoShin et al ldquoGRB 091024Aand the nature of ultra-long gamma-ray burstsrdquo AstrophysicalJournal vol 778 no 1 article 54 2013

[61] G Stratta B Gendre J L Atteia et al ldquoThe ultra-long GRB111209A II Prompt to afterglow and afterglow propertiesrdquoTheAstrophysical Journal vol 779 no 1 article 66 2013

[62] A J Levan N R Tanvir R L C Starling et al ldquoA newpopulation of ultra-long duration gamma-ray burstsrdquo TheAstrophysical Journal vol 781 no 1 article 13 2014

[63] P A Evans R Willingale J P Osborne et al ldquoGRB 130925Aan ultralong gamma ray burst with a dust-echo afterglow andimplications for the origin of the ultralong GRBsrdquo MonthlyNotices of the RoyalAstronomical Society vol 444 no 1 pp 250ndash267 2014

[64] B Gendre and G Stratta ldquoModels and possible progenitors ofgamma-ray bursts at the test field of the observationsrdquo Proceed-ings of the Rencontres deMoriond 2013 VeryHigh Energy Phe-nomena in the Universe session httparxivorgabs13053194

[65] D Nakauchi K Kashiyama Y Suwa and T NakamuraldquoBlue supergiant model for ultra-long gamma-ray burst withsuperluminous-supernova-like bumprdquo The Astrophysical Jour-nal vol 778 no 1 article 67 2013

[66] B-B Zhang B Zhang K Murase V Connaughton and MS Briggs ldquoHow long does a burst burstrdquo The AstrophysicalJournal vol 787 no 1 article 66 2014

[67] H Gao and P Meszaros ldquoRelation between the intrinsic andobserved central engine activity time implications for ultra-longGRBsrdquoTheAstrophysical Journal vol 802 no 2 p 90 2014

[68] D Band J Matteson L Ford et al ldquoBATSE observations ofgamma-ray burst spectra I Spectral diversityrdquo AstrophysicalJournal Letters vol 413 no 1 pp 281ndash292 1993

[69] Y Kaneko R D Preece M S Briggs W S Paciesas CA Meegan and D L Band ldquoThe complete spectral catalogof bright batse gamma-ray burstsrdquo The Astrophysical JournalSupplement Series vol 166 no 1 pp 298ndash340 2006

[70] L Nava G Ghirlanda G Ghisellini and A Celotti ldquoSpectralproperties of 438 GRBs detected by FermiGBMrdquo Astronomy ampAstrophysics vol 530 article 21 2011

[71] A Goldstein J M Burgess R D Preece et al ldquoThe fermiGBM gamma-ray burst spectral catalog the first two yearsrdquoTheAstrophysical Journal vol 199 no 1 article 19 2012

[72] A Goldstein R D Preece R S Mallozzi et al ldquoThe BATSE5B gamma-ray burst spectral catalogrdquoAstrophysical Journal vol208 no 2 article 21 2013

[73] R D Preece M S Briggs R S Mallozzi G N Pendleton W SPaciesas andD L Band ldquoTheBATSEgamma-rayBurst spectralcatalog I High time resolution spectroscopy of bright Burstsusing high energy resolution datardquo The Astrophysical Journalvol 126 no 1 pp 19ndash36 2000

[74] L Nava G Ghirlanda G Ghisellini and A CelottildquoFermiGBM and BATSE gamma-ray bursts comparisonof the spectral propertiesrdquo Monthly Notices of the RoyalAstronomical Society vol 415 no 4 pp 3153ndash3162 2011

[75] B-B Zhang E-W Liang Y-Z Fan et al ldquoA comprehensiveanalysis of fermi gamma-ray burst data I Spectral componentsand the possible physical origins of LATGBM GRBsrdquo TheAstrophysical Journal vol 730 no 2 article 141 2011

[76] D Gruber A Goldstein V W von Ahlefeld et al ldquoThe FermiGBM gamma-ray burst spectral catalog four years of datardquoAstrophysical Journal Supplement Series vol 211 no 1 article12 2014

[77] J Goodman ldquoAre gamma-ray bursts optically thickrdquo TheAstrophysical Journal vol 308 pp 47ndash50 1986

[78] B Paczynski ldquoGamma-ray bursters at cosmological distancesrdquoThe Astrophysical Journal vol 308 pp L43ndashL46 1986

[79] M Tavani ldquoA shock emission model for gamma-ray bursts IISpectral propertiesrdquo The Astrophysical Journal vol 466 no 2pp 768ndash778 1996

[80] E Cohen J I Katz T Piran R Sari R D Preece and D LBand ldquoPossible evidence for relativistic shocks in gamma-rayburstsrdquo The Astrophysical Journal vol 488 no 1 pp 330ndash3371997

[81] A Panaitescu M Spada and P Meszaros ldquoPower densityspectra of gamma-ray bursts in the internal shock modelrdquo TheAstrophysical Journal vol 522 no 2 pp L105ndashL108 1999

[82] F Frontera L Amati E Costa et al ldquoPrompt and delayed emis-sion properties of gamma-ray bursts observed with BeppoSAXrdquoThe Astrophysical Journal vol 127 no 1 pp 59ndash78 2000

[83] B A Crider E P Liang I A Smith et al ldquoEvolution of thelow-energy photon spectra in gamma-ray burstsrdquo AstrophysicalJournal Letters vol 479 no 1 pp L39ndashL42 1997

[84] R D Preece M S Briggs R S Mallozzi G N PendletonW S Paciesas and D L Band ldquoThe synchrotron shock modelconfronts a lsquoLine of deathrsquo in the BATSE gamma-ray burst datardquoThe Astrophysical Journal Letters vol 506 no 1 pp L23ndashL261998

[85] RD PreeceM S Briggs TWGibun et al ldquoOn the consistencyof gamma-ray burst spectral indices with the synchrotron shockmodelrdquoThe Astrophysical Journal vol 581 no 2 pp 1248ndash12552002

[86] G Ghirlanda A Celotti and G Ghisellini ldquoExtremely hardGRB spectra prune down the forest of emission modelsrdquoAstronomy and Astrophysics vol 406 no 3 pp 879ndash892 2003

[87] F Ryde ldquoThe cooling behavior of thermal pulses in gamma-rayburstsrdquo The Astrophysical Journal vol 614 no 2 pp 827ndash8462004

[88] F Ryde ldquoIs thermal emission in gamma-ray bursts ubiquitousrdquoThe Astrophysical Journal Letters vol 625 no 2 pp L95ndashL982005

[89] F Ryde andA Persquoer ldquoQuasi-blackbody component and radiativeefficiency of the prompt emission of gamma-ray burstsrdquo Astro-physical Journal Letters vol 702 no 2 pp 1211ndash1229 2009

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Biophysics

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ThermodynamicsJournal of

28 Advances in Astronomy

[90] S McGlynn S Foley B McBreen et al ldquoHigh energy emissionand polarisation limits for the INTEGRAL burst GRB 061122rdquoAstronomy amp Astrophysics vol 499 no 2 pp 465ndash472 2009

[91] J Larsson F Ryde C Lundman et al ldquoSpectral componentsin the bright long GRB061007 properties of the photosphereand the nature of the outflowrdquo Monthly Notices of the RoyalAstronomical Society vol 414 no 3 pp 2642ndash2649 2011

[92] G Ghirlanda Z Bosnjak G Ghisellini F Tavecchio andC Firmani ldquoBlackbody components in gamma-ray burstsspectrardquoMonthly Notices of the Royal Astronomical Society vol379 no 1 pp 73ndash85 2007

[93] F Frontera L Amati R Farinelli et al ldquoComptonizationsignatures in the prompt emission of gamma-ray burstsrdquoAstrophysical Journal vol 779 no 2 article 175 2013

[94] M Ackermann K Asano W B Atwood et al ldquoFermi obser-vations of GRB 090510 a short-hard gamma-ray burst with anadditional hard power-law component from 10 keV to GeVenergiesrdquo The Astrophysical Journal vol 716 no 2 pp 1178ndash1190 2010

[95] A A Abdo M Ackermann M Ajello et al ldquoFermi obser-vations of GRB 090902B a distinct spectral component inthe prompt and delayed emissionrdquo The Astrophysical JournalLetters vol 706 no 1 pp L138ndashL144 2009

[96] F Ryde M Axelsson B B Zhang et al ldquoIdentification andproperties of the photospheric emission in GRB090902Brdquo TheAstrophysical Journal Letters vol 709 no 2 pp L172ndashL177 2010

[97] F Ryde A Persquoer T Nymark et al ldquoObservational evidence ofdissipative photospheres in gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 415 no 4 pp 3693ndash37052011

[98] M Axelsson L Baldini G Barbiellini et al ldquoGRB110721Aan extreme peak energy and signatures of the photosphererdquoAstrophysical Journal Letters vol 757 no 2 article L31 2012

[99] S Iyyani F Ryde M Axelsson et al ldquoVariable jet propertiesin GRB 110721A time resolved observations of the jet photo-sphererdquo Monthly Notices of the Royal Astronomical Society vol433 no 4 pp 2739ndash2748 2013

[100] S Guiriec V Connaughton M S Briggs et al ldquoDetection ofa thermal spectral component in the prompt emission of GRB100724BrdquoTheAstrophysical Journal Letters vol 727 no 2 articleL33 2011

[101] G Ghirlanda A Pescalli and G Ghisellini ldquoPhotosphericemission throughout grb 100507 detected by fermirdquo MonthlyNotices of the Royal Astronomical Society vol 432 no 4 pp3237ndash3244 2013

[102] S Guiriec F Daigne R Hascoet et al ldquoEvidence for aphotospheric component in the prompt emission of the shortGRB 120323a and its effects on the GRB hardness-luminosityrelationrdquo The Astrophysical Journal vol 770 no 1 article 322013

[103] R Basak and A R Rao ldquoTime-resolved spectral study of Fermigamma-ray bursts having single pulsesrdquoMonthly Notices of theRoyal Astronomical Society vol 442 no 1 pp 419ndash427 2014

[104] W Deng and B Zhang ldquoLow energy spectral index and Epevolution of quasi-thermal photosphere emission of gamma-ray burstsrdquoThe Astrophysical Journal vol 785 no 2 article 1122014

[105] S Guiriec C Kouveliotou F Daigne et al ldquoTowards a betterunderstanding of the GRB phenomenon a new model for GRBprompt emission and its effects on the newNon55Thermal119871NTi -119864restNTpeaki relationrdquo httparxivorgabs150107028

[106] J M Burgess R D Preece V Connaughton et al ldquoTime-resolved analysis of fermi gamma-ray burstswith fast- and slow-cooled synchrotron photon modelsrdquoThe Astrophysical Journalvol 784 no 1 article 17 2014

[107] H-F Yu J Greiner H van Eerten et al ldquoSynchrotron coolingin energetic gamma-ray bursts observed by the fermi gamma-ray burst monitorrdquo Astronomy amp Astrophysics vol 573 no 8120 pages 2015

[108] J M Burgess F Ryde and H-F Yu ldquoTaking the band functiontoo far a tale of two 120572rsquosrdquo httparxivorgabs14107647

[109] M Axelsson and L Borgonovo ldquoThe width of gamma-ray burstspectrardquoMonthly Notices of the Royal Astronomical Society vol447 no 4 pp 3150ndash3154 2015

[110] R Preece J M Burgess A von Kienlin et al ldquoThe first pulseof the extremely bright GRB 130427a a test lab for synchrotronshocksrdquo Science vol 343 no 6166 pp 51ndash54 2014

[111] A A Abdo M Ackermann M Ajello et al ldquoA limit on thevariation of the speed of light arising from quantum gravityeffectsrdquo Nature vol 462 no 7271 pp 331ndash334 2009

[112] P Kumar and R B Duran ldquoExternal forward shock origin ofhigh-energy emission for three gamma-ray bursts detected byFermirdquo Monthly Notices of the Royal Astronomical Society vol409 no 1 pp 226ndash236 2010

[113] G Ghirlanda G Ghisellini and L Nava ldquoThe onset of the GeVafterglow of GRB 090510rdquoAstronomy and Astrophysics vol 510no 1 article L7 2010

[114] M Ackermann M Ajello K Asano et al ldquoThe first Fermi-Latgamma-ray burst catalogrdquo Astrophysical Journal SupplementSeries vol 209 no 1 article 11 2013

[115] L Nava G Vianello N Omodei et al ldquoClustering of LAT lightcurves a clue to the origin of high-energy emission in gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 443 no 4 pp 3578ndash3585 2014

[116] J L Racusin S V Karpov M Sokolowski et al ldquoBroadbandobservations of the naked-eye 120574-ray burst GRB 080319BrdquoNature vol 455 no 7210 pp 183ndash188 2008

[117] C Akerlof R Balsano S Barthelmy et al ldquoObservation ofcontemporaneous optical radiation from a 120574-ray burstrdquoNaturevol 398 no 6726 pp 400ndash402 1999

[118] G B Rybicki and A P Lightman Radiative Processes inAstrophysics 1979

[119] S Covino D Lazzati G Ghisellini et al ldquoGRB 990510 linearlypolarized radiation from a fireballrdquo Astronomy amp Astrophysicsvol 348 pp L1ndashL4 1999

[120] R AM JWijers PM Vreeswijk T J Galama et al ldquoDetectionof polarization in the afterglow of GRB 990510 with the ESOvery large telescoperdquoThe Astrophysical Journal Letters vol 523no 1 pp L33ndashL36 1999

[121] A Loeb and R Perna ldquoMicrolensing of gamma-ray burstafterglowsrdquo The Astrophysical Journal vol 495 no 2 pp 597ndash603 1998

[122] A Gruzinov and E Waxman ldquoGamma-ray burst afterglowpolarization and analytic light curvesrdquo The Astrophysical Jour-nal vol 511 no 2 pp 852ndash861 1999

[123] G Ghisellini and D Lazzati ldquoPolarization light curves andposition angle variation of beamed gamma-ray burstsrdquoMonthlyNotices of the Royal Astronomical Society vol 309 no 1 pp L7ndashL11 1999

[124] M V Medvedev and A Loeb ldquoGeneration of magnetic fieldsin the relativistic shock of gamma-ray burst sourcesrdquo TheAstrophysical Journal vol 526 no 2 pp 697ndash706 1999

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 29

[125] J Granot and A Konigl ldquoLinear polarization in gamma-raybursts the case for an orderedmagnetic fieldrdquoTheAstrophysicalJournal vol 594 no 2 pp 83ndash87 2003

[126] W Coburn and S E Boggs ldquoPolarization of the prompt 120574-rayemission from the 120574-ray burst of 6 December 2002rdquoNature vol423 no 6938 pp 415ndash417 2003

[127] R E Rutledge and D B Fox ldquoRe-analysis of polarization inthe 120574-ray flux of GRB 021206rdquo Monthly Notices of the RoyalAstronomical Society vol 350 no 4 pp 1288ndash1300 2004

[128] D R Willis E J Barlow A J Bird et al ldquoEvidence ofpolarisation in the prompt gamma-ray emission from GRB930131 and GRB 960924rdquo Astronomy and Astrophysics vol 439no 1 pp 245ndash253 2005

[129] E Kalemci S E Boggs C Kouveliotou M Finger and MG Baring ldquoSearch for polarization from the prompt gamma-ray emission of GRB 041219a with SPI on INTEGRALrdquo TheAstrophysical Journal vol 169 no 1 pp 75ndash82 2007

[130] S McGlynn D J Clark A J Dean et al ldquoPolarisation studies ofthe prompt gamma-ray emission from GRB 041219a using thespectrometer aboard INTEGRALrdquoAstronomy andAstrophysicsvol 466 no 3 pp 895ndash904 2007

[131] D Gotz P Laurent F Lebrun F Daigne and Z BosnjakldquoVariable polarization measured in the prompt emission ofGRB 041219a using ibis on board integralrdquoAstrophysical JournalLetters vol 695 no 2 pp L208ndashL212 2009

[132] D Yonetoku T Murakami S Gunji et al ldquoDetection ofGamma-Ray polarization in prompt emission ofGRB 100826ArdquoThe Astrophysical Journal vol 743 no 2 article L30 2011

[133] D Yonetoku T Murakami S Gunji et al ldquoMagnetic structuresin gamma-ray burst jets probed by gamma-ray polarizationrdquoThe Astrophysical Journal Letters vol 758 no 1 article L1 2012

[134] J Granot Fermi LAT Collaboration and GBM Collabora-tion ldquoHighlights from Fermi GRB observationsrdquo in Pro-ceedings of the Shocking UniversemdashGamma-Ray Bursts andHigh Energy Shock Phenomena Venice Italy September 2009httparxivorgabs10032452

[135] R Atkins W Benbow D Berley et al ldquoEvidence for TeVemission from GRB 970417ardquo Astrophysical Journal Letters vol533 no 2 pp L119ndashL122 2000

[136] J Albert E Aliu H Anderhub et al ldquoVery high energy gamma-ray radiation from the stellar mass black hole binary cygnus X-1rdquo The Astrophysical Journal Letters vol 665 no 1 pp 51ndash542007

[137] J Aleksic S Ansoldi L AAntonelli et al ldquoMAGICupper limitson the GRB 090102 afterglowrdquo Monthly Notices of the RoyalAstronomical Society vol 437 no 4 pp 3103ndash3111 2014

[138] P M S Parkinson and B L Dingus ldquoA search for promptvery high energy emission from satellite-detected gamma-raybursts using milagrordquo in Proceedings of the 30th InternationalCosmic Ray Conference R Caballero J C DrsquoOlivo G Medina-Tanco LNellen F A Sanchez and J F Valdes-Galicia Eds vol3 pp 1187ndash1190 Universidad Nacional Autonoma de MexicoYucatan Mexico July 2007

[139] F Aharonian A G Akhperjanian U B de Almeida et alldquoHESS observations of the prompt and afterglow phases of GRB060602Brdquo The Astrophysical Journal vol 690 no 2 pp 1068ndash1073 2009

[140] F Aharonian A G Akhperjanian U Barres de Almeida et alldquoHESS observations of 120574-ray bursts in 2003ndash2007rdquo Astronomyamp Astrophysics vol 495 pp 505ndash512 2009

[141] H E S S Collaboration A Abramowski F Aharonian et alldquoSearch for TeV gamma-ray emission from GRB 100621A anextremely bright GRB in X-rays with HESSrdquo Astronomy ampAstrophysics vol 565 article A16 6 pages 2014

[142] V A Acciari E Aliu T Arlen et al ldquoVeritas observations ofgamma-ray bursts detected by Swiftrdquo Astrophysical Journal vol743 no 1 article 62 2011

[143] A U Abeysekara R Alfaro C Alvarez et al ldquoSearch forgamma-rays from the unusually bright GRB 130427A with theHAWC gamma-ray observatoryrdquoTheAstrophysical Journal vol800 no 2 p 78 2015

[144] C H Blake J S Bloom D L Starr et al ldquoAn infrared flashcontemporaneous with the -rays of GRB 041219ardquo Nature vol435 no 7039 pp 181ndash184 2005

[145] P Romano S Campana G Chincarini et al ldquoPanchromaticstudy of GRB 060124 from precursor to afterglowrdquo Astronomyamp Astrophysics vol 456 no 3 pp 917ndash927 2006

[146] K L Page R Willingale J P Osborne et al ldquoGRB 061121broadband spectral evolution through the prompt and after-glow phases of a bright burstrdquo The Astrophysical Journal vol663 no 2 pp 1125ndash1138 2007

[147] C Guidorzi S Kobayashi D A Perley et al ldquoA faint opticalflash in dust-obscured GRB 080603A implications for GRBprompt emission mechanismsrdquo Monthly Notices of the RoyalAstronomical Society vol 417 no 3 pp 2124ndash2143 2011

[148] A Rossi S Schulze S Klose et al ldquoThe swiftfermiGRB080928from 1 eV to 150 keVrdquoAstronomyampAstrophysics vol 529 articleA142 2011

[149] D Kopac S Kobayashi A Gomboc et al ldquoGRB 090727 andgamma-ray bursts with early-time optical emissionrdquoAstrophys-ical Journal vol 772 no 1 article 73 2013

[150] J Elliott H-F Yu S Schmidl et al ldquoPrompt emission of GRB121217A from gamma-rays to the near-infraredrdquo Astronomy ampAstrophysics vol 562 article 100 2014

[151] A Maselli A Melandri L Nava et al ldquoGRB 130427A a nearbyordinary monsterrdquo Science vol 343 no 6166 pp 48ndash51 2014

[152] J Greiner H-F Yu T Kruhler et al ldquoGROND coverage ofthe main peak of gamma-ray burst 130925Ardquo Astronomy ampAstrophysics vol 568 p A75 2014

[153] W T Vestrand J A Wren P R Wozniak et al ldquoEnergy inputand response from prompt and early optical afterglow emissionin 120574-ray burstsrdquo Nature vol 442 no 7099 pp 172ndash175 2006

[154] W Zheng R F Shen T Sakamoto et al ldquoPanchromatic obser-vations of the textbook GRB 110205A constraining physicalmechanisms of prompt emission and afterglowrdquoThe Astrophys-ical Journal vol 751 no 2 article 90 2012

[155] S V Golenetskii E P Mazets R L Aptekar and V N IlyinskiildquoCorrelation between luminosity and temperature in 120574-rayburst sourcesrdquo Nature vol 306 no 5942 pp 451ndash453 1983

[156] V E Kargatis E P Liang K C Hurley C Barat E Eveno andM Niel ldquoSpectral evolution of gamma-ray bursts detected bythe SIGNE experiment I Correlation between intensity andspectral hardnessrdquo Astrophysical Journal Letters vol 422 no 1pp 260ndash268 1994

[157] L Amati F Frontera M Tavani et al ldquoIntrinsic spectraand energetics of BeppoSAX gamma-ray bursts with knownredshiftsrdquoAstronomy and Astrophysics vol 390 no 1 pp 81ndash892002

[158] L Amati ldquoThe Epi-Eiso correlation in gamma-ray burstsupdated observational status re-analysis and main implica-tionsrdquo Monthly Notices of the Royal Astronomical Society vol372 no 1 pp 233ndash245 2006

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in Condensed Matter Physics

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Superconductivity

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AstrophysicsJournal of

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 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

30 Advances in Astronomy

[159] F Frontera L Amati C Guidorzi R Landi and J InrsquoT ZandldquoBroadband time-resolved Epi-Liso correlation in gamma-rayburstsrdquo The Astrophysical Journal vol 754 no 2 article 1382012

[160] E Nakar and T Piran ldquoOutliers to the peak energy-isotropicenergy relation in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 360 no 1 pp L73ndashL76 2005

[161] D L Band and R D Preece ldquoTesting the gamma-ray burstenergy relationshipsrdquo Astrophysical Journal Letters vol 627 no1 pp 319ndash323 2005

[162] N R Butler D Kocevski J S Bloom and J L CurtisldquoA complete catalog of Swift gamma-ray burst spectra anddurations demise of a physical origin for pre-Swift high-energycorrelationsrdquo Astrophysical Journal vol 671 no 1 pp 656ndash6772007

[163] N R Butler D Kocevski and J S Bloom ldquoGeneralized tests forselection effects in gamma-ray burst high-energy correlationsrdquoAstrophysical Journal Letters vol 694 no 1 pp 76ndash83 2009

[164] A Shahmoradi and R J Nemiroff ldquoThe possible impact ofgamma-ray burst detector thresholds on cosmological standardcandlesrdquoMonthly Notices of the Royal Astronomical Society vol411 no 3 pp 1843ndash1856 2011

[165] A C Collazzi B E Schaefer and J A Moree ldquoThe totalerrors inmeasuring e peak for gamma-ray burstsrdquoAstrophysicalJournal vol 729 no 2 article 89 2011

[166] D Kocevski ldquoOn the origin of high-energy correlations ingamma-ray burstsrdquoThe Astrophysical Journal vol 747 no 2 p146 2012

[167] G Ghirlanda G Ghisellini and C Firmani ldquoProbing theexistence of theE

119901119890119886119896-E119894119904119900correlation in long gamma ray burstsrdquo

Monthly Notices of the Royal Astronomical Society vol 361 no1 pp L10ndashL14 2005

[168] G Ghirlanda L Nava G Ghisellini C Firmani and J ICabrera ldquoThe Epeak-Eiso plane of long gamma-ray bursts andselection effectsrdquo Monthly Notices of the Royal AstronomicalSociety vol 387 no 1 pp 319ndash330 2008

[169] G Ghirlanda G Ghisellini L Nava et al ldquoThe impact ofselection biases on the Epeak-Liso correlation of gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol422 pp 2553ndash2559 2012

[170] L Nava R Salvaterra G Ghirlanda et al ldquoA complete sample ofbright Swift long gamma-ray bursts testing the spectral-energycorrelationsrdquoMonthly Notices of the Royal Astronomical Societyvol 421 no 2 pp 1256ndash1264 2012

[171] R Basak and A R Rao ldquoPulse-wise Amati correlation in Fermigamma-ray burstsrdquo Monthly Notices of the Royal AstronomicalSociety vol 436 no 4 pp 3082ndash3088 2013

[172] F J Virgili Y Qin B Zhang and E Liang ldquoSpectral andtemporal analysis of the joint SwiftBAT-FermiGBM GRBsamplerdquoMonthly Notices of the Royal Astronomical Society vol424 no 4 pp 2821ndash2831 2012

[173] V Heussaff J-L Atteia and Y Zolnierowski ldquoThe Epeak-Eisorelation revisited with fermi GRBs resolving a long-standingdebaterdquo Astronomy amp Astrophysics vol 557 article 100 2013

[174] D M Wei and W H Gao ldquoAre there cosmological evolutiontrends on gamma-ray burst featuresrdquo Monthly Notices of theRoyal Astronomical Society vol 345 no 3 pp 743ndash746 2003

[175] D Yonetoku T Murakami T Nakamura R Yamazaki A KInoue and K Ioka ldquoGamma-ray burst formation rate inferredfrom the spectral peak energy-peak luminosity relationrdquo TheAstrophysical Journal vol 609 no 2 pp 935ndash951 2004

[176] G Ghirlanda G Ghisellini and D Lazzati ldquoThe collimation-corrected gamma-ray burst energies correlate with the peakenergy of their ]F] spectrumrdquoAstrophysical Journal Letters vol616 no 1 pp 331ndash338 2004

[177] G Ghisellini G Ghirlanda L Nava and C Firmani ldquolsquoLatepromptrsquo emission in gamma-ray burstsrdquo Astrophysical Journalvol 658 no 2 pp L75ndashL78 2007

[178] E-W Liang J L Racusin B Zhang B-B Zhang and D NBurrows ldquoA comprehensive analysis of Swift XRT data III Jetbreak candidates in X-ray and optical afterglow light curvesrdquoThe Astrophysical Journal vol 675 no 1 pp 528ndash552 2008

[179] D Kocevski and N Butler ldquoGamma-ray burst energetics in theSwift ERArdquo The Astrophysical Journal vol 680 no 1 pp 531ndash538 2008

[180] J L Racusin E W Liang D N Burrows et al ldquoJet breaksand energetics of swift gamma-ray burst X-ray afterglowsrdquoTheAstrophysical Journal vol 698 no 1 pp 43ndash74 2009

[181] G Ryan H van Eerten A MacFadyen and B-B ZhangldquoGamma-ray bursts are observed off-axisrdquo The AstrophysicalJournal vol 799 no 1 article 3 2015

[182] R J Nemiroff ldquoA century of gamma ray burst modelsrdquo Com-ments on Astrophysics vol 17 p 189 1994

[183] D Eichler M Livio T Piran and D N Schramm ldquoNucle-osynthesis neutrino bursts and 120574-rays from coalescing neutronstarsrdquo Nature vol 340 no 6229 pp 126ndash128 1989

[184] B Paczynski ldquoSuper-Eddington winds from neutron starsrdquoAstrophysical Journal vol 363 no 1 pp 218ndash226 1990

[185] R Narayan T Piran and A Shemi ldquoNeutron star and blackhole binaries in the Galaxyrdquo Astrophysical Journal Letters vol379 no 1 pp L17ndashL20 1991

[186] P Meszaros and M J Rees ldquoTidal heating and mass lossin neutron star binaries implications for gamma-ray burstmodelsrdquoThe Astrophysical Journal vol 397 no 2 pp 570ndash5751992

[187] R Narayan B Paczynski and T Piran ldquoGamma-ray burstsas the death throes of massive binary starsrdquo The AstrophysicalJournal vol 395 no 2 pp 83ndash86 1992

[188] S E Woosley ldquoGamma-ray bursts from stellar mass accretiondisks around black holesrdquo The Astrophysical Journal vol 405no 1 pp 273ndash277 1993

[189] B Paczynski ldquoAre gamma-ray bursts in star-forming regionsrdquoThe Astrophysical Journal Letters vol 494 no 1 pp L45ndashL481998

[190] B Paczynski ldquoGamma-ray bursts as hypernovaerdquo inProceedingsof the 4th Huntsville Gamma-Ray Burst Symposium C AMeegan R D Preece and T M Koshut Eds vol 428 ofAmerican Institute of Physics Conference Series pp 783ndash787Huntsville Ala USA May 1998

[191] C L Fryer S E Woosley and D H Hartmann ldquoFormationrates of black hole accretion disk gamma-ray burstsrdquo TheAstrophysical Journal vol 526 no 1 pp 152ndash177 1999

[192] A I MacFadyen and S E Woosley ldquoCollapsars gamma-ray bursts and explosions in lsquofailed supernovaersquordquo AstrophysicalJournal Letters vol 524 no 1 pp 262ndash289 1999

[193] R Popham S E Woosley and C Fryer ldquoHyperaccreting blackholes and gamma-ray burstsrdquoTheAstrophysical Journal vol 518no 1 pp 356ndash374 1999

[194] S EWoosley and J S Bloom ldquoThe supernova-gamma-ray burstconnectionrdquoAnnual Review of Astronomy and Astrophysics vol44 pp 507ndash556 2006

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in Condensed Matter Physics

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Superconductivity

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AstrophysicsJournal of

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Physics Research International

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 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

Advances in Astronomy 31

[195] G Cavallo and M J Rees ldquoA qualitative study of cosmicfireballs and gamma-ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 183 no 3 pp 359ndash365 1978

[196] V V Usov ldquoOn the nature of nonthermal radiation fromcosmological gamma-ray burstersrdquoMonthly Notices of the RoyalAstronomical Society vol 267 p 1035 1994

[197] CThompson ldquoA model of gamma-ray burstsrdquoMonthly Noticesof the Royal Astronomical Society vol 270 p 480 1994

[198] J I Katz ldquoYet another model of gamma-ray burstsrdquo TheAstrophysical Journal vol 490 no 2 pp 633ndash641 1997

[199] P Meszaros and M J Rees ldquoPoynting jets from black holes andcosmological gamma-ray burstsrdquo Astrophysical Journal Lettersvol 482 no 1 pp L29ndashL32 1997

[200] M Lyutikov and R Blandford ldquoGamma ray bursts as electro-magnetic outflowsrdquo httparxivorgabsastro-ph0312347

[201] B Zhang andH Yan ldquoThe internal-collision-inducedmagneticreconnection and turbulence (ICMART) model of gamma-rayburstsrdquoThe Astrophysical Journal vol 726 no 2 p 90 2011

[202] A Shemi and T Piran ldquoThe appearance of cosmic fireballsrdquoAstrophysical Journal vol 365 no 2 pp L55ndashL58 1990

[203] J H Krolik and E A Pier ldquoRelativistic motion in gamma-rayburstsrdquo The Astrophysical Journal vol 373 no 1 pp 277ndash2841991

[204] E E Fenimore R I Epstein and CHo ldquoThe escape of 100MeVphotons from cosmological gammaray burstsrdquo Astronomy andAstrophysics Supplement Series vol 97 no 1 pp 59ndash62 1993

[205] E Woods and A Loeb ldquoEmpirical constraints on source prop-erties and host galaxies of cosmological gamma-ray burstsrdquoTheAstrophysical Journal vol 453 no 2 pp 583ndash595 1995

[206] M G Baring and A K Harding ldquoThe escape of high-energyphotons fromgamma-ray burstsrdquoTheAstrophysical Journal vol491 no 2 pp 663ndash686 1997

[207] R Sari and T Piran ldquoGRB 990123 the optical flash and thefireball modelrdquoThe Astrophysical Journal Letters vol 517 no 2pp L109ndashL112 1999

[208] Y Lithwick and R Sari ldquoLower limits on Lorentz factors ingamma-ray burstsrdquo Astrophysical Journal Letters vol 555 no1 pp 540ndash545 2001

[209] B Zhang S Kobayashi and P Meszaros ldquoGamma-ray burstearly optical afterglows implications for the initial lorentz factorand the central enginerdquo The Astrophysical Journal vol 595 no2 pp 950ndash954 2003

[210] EMolinari S DVergani DMalesani et al ldquoREMobservationsof GRB060418 and GRB 060607A the onset of the afterglowand the initial fireball Lorentz factor determinationrdquoAstronomyand Astrophysics vol 469 no 1 pp 13ndash16 2007

[211] E-W Liang S-X Yi J Zhang H-J Lu and B-B ZhangldquoConstraining gamma-ray burst initial lorentz factor withthe afterglow onset feature and discovery of a tight Γ

0-119864120574iso

CorrelationrdquoTheAstrophysical Journal vol 725 pp 2209ndash22242010

[212] J L Racusin S R Oates P Schady et al ldquoFERMI and Swiftgamma-ray burst afterglow population studiesrdquoThe Astrophys-ical Journal vol 738 no 2 article 138 2011

[213] P Meszaros P Laguna and M J Rees ldquoGasdynamics ofrelativistically expanding gamma-ray burst sources kinematicsenergeticsmagnetic fields and efficiencyrdquoAstrophysical JournalLetters vol 415 no 1 pp 181ndash190 1993

[214] B Paczynski and G Xu ldquoNeutrino bursts from gamma-rayburstsrdquo Astrophysical Journal vol 427 no 2 pp 708ndash713 1994

[215] M J Rees and P Meszaros ldquoUnsteady outflow models forcosmological gamma-ray burstsrdquoTheAstrophysical Journal vol430 no 2 pp L93ndashL96 1994

[216] R Sari and T Piran ldquoVariability in gamma-ray bursts a cluerdquoThe Astrophysical Journal vol 485 no 1 pp 270ndash273 1997

[217] S Kobayashi T Piran andR Sari ldquoCan internal shocks producethe variability in gamma-ray burstsrdquo Astrophysical JournalLetters vol 490 no 1 pp 92ndash98 1997

[218] F Daigne and R Mochkovitch ldquoGamma-ray bursts frominternal shocks in a relativistic wind temporal and spectralpropertiesrdquo Monthly Notices of the Royal Astronomical Societyvol 296 no 2 pp 275ndash286 1998

[219] R Mochkovitch V Maitia and R Marques ldquoInternal shocksin a relativistic wind as a source for gamma-ray burstsrdquoAstrophysics and Space Science vol 231 no 1-2 pp 441ndash4441995

[220] D Lazzati G Ghisellini and A Celotti ldquoConstraints on thebulk Lorentz factor in the internal shock scenario for gamma-ray burstsrdquo Monthly Notices of the Royal Astronomical Societyvol 309 no 2 pp L13ndashL17 1999

[221] P Kumar ldquoGamma-ray burst energeticsrdquo The AstrophysicalJournal vol 523 no 2 pp L113ndashL116 1999

[222] M Spada A Panaitescu and PMeszaros ldquoAnalysis of temporalfeatures of gamma-ray bursts in the internal shock modelrdquoTheAstrophysical Journal vol 537 no 2 pp 824ndash832 2000

[223] D Guetta M Spada and EWaxman ldquoEfficiency and spectrumof internal gamma-ray burst shocksrdquoThe Astrophysical Journalvol 557 no 1 pp 399ndash407 2001

[224] A Maxham and B Zhang ldquoModeling gamma-ray burst X-ray flares within the internal shock modelrdquo The AstrophysicalJournal vol 707 no 2 pp 1623ndash1633 2009

[225] NM Lloyd-Ronning and B Zhang ldquoOn the kinetic energy andradiative efficiency of gamma-ray burstsrdquo Astrophysical JournalLetters vol 613 no 1 pp 477ndash483 2004

[226] K Ioka K Toma R Yamazaki and T Nakamura ldquoEfficiencycrisis of swift gamma-ray bursts with shallow X-ray afterglowsprior activity or time-dependent microphysicsrdquo Astronomyand Astrophysics vol 458 no 1 pp 7ndash12 2006

[227] A Nousek C Kouveliotou D Grupe et al ldquoEvidence for acanonical gamma-ray burst afterglow light curve in the SwiftXRT datardquo The Astrophysical Journal vol 642 no 1 pp 389ndash400 2006

[228] B Zhang E Liang K L Page et al ldquoGRB radiative efficienciesderived from the Swift data GRBs versus XRFs long versusshortrdquo The Astrophysical Journal vol 655 no 2 pp 989ndash10012007

[229] A Persquoer B-B Zhang F Ryde S Mcglynn R D Preece andC Kouveliotou ldquoThe connection between thermal and non-thermal emission in gamma-ray bursts general considerationsand GRB 090902B as a case studyrdquoMonthly Notices of the RoyalAstronomical Society vol 420 no 1 pp 468ndash482 2012

[230] A M Beloborodov ldquoOn the efficiency of internal shocks ingamma-ray burstsrdquo Astrophysical Journal Letters vol 539 no1 pp L25ndashL28 2000

[231] S Kobayashi and R Sari ldquoUltraefficient internal shocksrdquoAstrophysical Journal Letters vol 551 no 2 pp 934ndash939 2001

[232] E V Derishev and V V Kocharovsky ldquoThe neutron componentin fireballs of gamma-ray bursts dynamics and observableimprintsrdquoTheAstrophysical Journal vol 521 no 2 pp 640ndash6491999

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

32 Advances in Astronomy

[233] J N Bahcall and P Meszaros ldquo5ndash10 GeV neutrinos fromgamma-ray burst fireballsrdquo Physical Review Letters vol 85 no7 pp 1362ndash1365 2000

[234] PMeszaros andM J Rees ldquoMulti-GeV neutrinos from internaldissipation in gamma-ray burst fireballsrdquo The AstrophysicalJournal Letters vol 541 no 1 pp L5ndashL8 2000

[235] E M Rossi A M Beloborodov and M J Rees ldquoNeutron-loaded outflows in gamma-ray burstsrdquo Monthly Notices of theRoyal Astronomical Society vol 369 no 4 pp 1797ndash1807 2006

[236] A M Beloborodov ldquoCollisional mechanism for gamma-rayburst emissionrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 2 pp 1033ndash1047 2010

[237] I Vurm A M Beloborodov and J Poutanen ldquoGamma-raybursts frommagnetized collisionally heated jetsrdquoTheAstrophys-ical Journal vol 738 no 1 article 77 2011

[238] M A Abramowicz I D Novikov and B Paczynski ldquoTheappearance of highly relativistic spherically symmetric stellarwindsrdquo The Astrophysical Journal vol 369 no 1 pp 175ndash1781991

[239] P Meszaros and M J Rees ldquoSteep slopes and preferred breaksin gamma-ray burst spectra the role of photospheres andcomptonizationrdquo The Astrophysical Journal vol 530 no 1 pp292ndash298 2000

[240] P Meszaros E Ramirez-Ruiz M J Rees and B Zhang ldquoX-ray-rich gamma-ray bursts photospheres and variabilityrdquo TheAstrophysical Journal vol 578 no 2 pp 812ndash817 2002

[241] A Persquoer ldquoTemporal evolution of thermal emission from rela-tivistically expanding plasmardquo The Astrophysical Journal vol682 no 1 pp 463ndash473 2008

[242] A M Beloborodov ldquoRadiative transfer in ultrarelativistic out-flowsrdquoThe Astrophysical Journal vol 737 no 2 p 68 2011

[243] A Persquoer and F Ryde ldquoA theory of multicolor blackbody emis-sion from relativistically expanding plasmasrdquoThe AstrophysicalJournal vol 732 no 1 article 49 2011

[244] C Lundman A Persquoer and F Ryde ldquoA theory of photosphericemission from relativistic collimated outflowsrdquoMonthlyNoticesof the Royal Astronomical Society vol 428 no 3 pp 2430ndash24422013

[245] B Zhang Y Z Fan J Dyks et al ldquoPhysical processes shap-ing gamma-ray burst X-ray afterglow light curves theoreticalimplications from the swift X-ray telescope observations rdquo TheAstrophysical Journal vol 642 no 1 pp 354ndash370 2006

[246] A Rowlinson P T Orsquobrien B D Metzger N R Tanvir and AJ Levan ldquoSignatures of magnetar central engines in short GRBlight curvesrdquoMonthly Notices of the Royal Astronomical Societyvol 430 no 2 pp 1061ndash1087 2013

[247] H van Eerten ldquoSelf-similar relativistic blast waves with energyinjectionrdquo Monthly Notices of the Royal Astronomical Societyvol 442 no 4 pp 3495ndash3510 2014

[248] H J van Eerten ldquoGamma-ray burst afterglow plateau breaktime-luminosity correlations favour thick shellmodels over thinshell modelsrdquoMonthly Notices of the Royal Astronomical Societyvol 445 no 3 pp 2414ndash2423 2014

[249] R D Blandford and R L Znajek ldquoElectromagnetic extractionof energy from Kerr black holesrdquo Monthly Notices of the RoyalAstronomical Society vol 179 no 3 pp 433ndash456 1977

[250] R D Blandford and D G Payne ldquoHydromagnetic flows fromaccretion discs and the production of radio jetsrdquo MonthlyNotices of the Royal Astronomical Society vol 199 no 4 pp 883ndash903 1982

[251] S S Komissarov ldquoDirect numerical simulations of theBlandford-Znajek effectrdquo Monthly Notices of the Royal Astro-nomical Society vol 326 no 3 pp L41ndashL44 2001

[252] D L Meier S Koide and Y Uchida ldquoMagnetohydrodynamicproduction of relativistic jetsrdquo Science vol 291 no 5501 pp 84ndash92 2001

[253] J C McKinney and C F Gammie ldquoA measurement of theelectromagnetic luminosity of a Kerr black holerdquo AstrophysicalJournal Letters vol 611 no 2 pp 977ndash995 2004

[254] S S Komissarov ldquoGeneral relativistic magnetohydrodynamicsimulations of monopole magnetospheres of black holesrdquoMonthly Notices of the Royal Astronomical Society vol 350 no4 pp 1431ndash1436 2004

[255] J C McKinney ldquoTotal and jet blandford-znajek power in thepresence of an accretion diskrdquoAstrophysical Journal Letters vol630 no 1 pp L5ndashL8 2005

[256] J C McKinney ldquoGeneral relativistic magnetohydrodynamicsimulations of the jet formation and large-scale propagationfrom black hole accretion systemsrdquoMonthly Notices of the RoyalAstronomical Society vol 368 no 4 pp 1561ndash1582 2006

[257] S S Komissarov ldquoMultidimensional numerical scheme forresistive relativistic magnetohydrodynamicsrdquo Monthly Noticesof the Royal Astronomical Society vol 382 no 3 pp 995ndash10042007

[258] A Tchekhovskoy J CMcKinney and R Narayan ldquoSimulationsof ultrarelativistic magnetodynamic jets from gamma-ray burstenginesrdquoMonthly Notices of the Royal Astronomical Society vol388 no 2 pp 551ndash572 2008

[259] A Tchekhovskoy R Narayan and J C McKinney ldquoBlack holespin and the radio loudquiet dichotomy of active galacticnucleirdquoTheAstrophysical Journal vol 711 no 1 pp 50ndash63 2010

[260] A Tchekhovskoy R Narayan and J C Mckinney ldquoEfficientgeneration of jets from magnetically arrested accretion ona rapidly spinning black holerdquo Monthly Notices of the RoyalAstronomical Society Letters vol 418 no 1 pp L79ndashL83 2011

[261] H C Spruit ldquoTheory of magnetically powered jetsrdquo in The JetParadigm T Belloni Ed vol 794 of Lecture Notes in Physics p233 Springer Berlin Germany 2010

[262] V V Usov ldquoMillisecond pulsars with extremely strongmagneticfields as a cosmological source of 120574-ray burstsrdquo Nature vol 357no 6378 pp 472ndash474 1992

[263] W Kluzniak andM Ruderman ldquoThe central engine of gamma-ray burstersrdquoTheAstrophysical Journal vol 505 no 2 pp L113ndashL117 1998

[264] H C Spruit ldquoGamma-ray bursts from X-ray binariesrdquo Astron-omy amp Astrophysics vol 341 pp L1ndashL4 1999

[265] J C Wheeler I Yi P Hoflich and L Wang ldquoAsymmetricsupernovae pulsars magnetars and gamma-ray burstsrdquo TheAstrophysical Journal vol 537 no 2 pp 810ndash823 2000

[266] T A Thompson P Chang and E Quataert ldquoMagnetar spin-down hyperenergetic supernovae and gamma-ray burstsrdquoTheAstrophysical Journal vol 611 no 1 I pp 380ndash393 2004

[267] D A Uzdensky and A I MacFadyen ldquoMagnetar-driven mag-netic tower as a model for gamma-ray bursts and asymmetricsupernovaerdquoThe Astrophysical Journal vol 669 no 1 pp 546ndash560 2007

[268] N Bucciantini E Quataert J Arons B D Metzger and TA Thompson ldquoRelativistic jets and long-duration gamma-raybursts from the birth ofmagnetarsrdquoMonthlyNotices of the RoyalAstronomical Society Letters vol 383 no 1 pp L25ndashL29 2008

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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FluidsJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

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AstronomyAdvances in

International Journal of

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Superconductivity

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Statistical MechanicsInternational Journal of

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GravityJournal of

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AstrophysicsJournal of

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Physics Research International

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Solid State PhysicsJournal of

 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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Biophysics

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ThermodynamicsJournal of

Advances in Astronomy 33

[269] N Bucciantini E Quataert B D Metzger T A Thompson JArons and L Del Zanna ldquoMagnetized relativistic jets and long-duration GRBs frommagnetar spin-down during core-collapsesupernovaerdquoMonthly Notices of the Royal Astronomical Societyvol 396 no 4 pp 2038ndash2050 2009

[270] S S Komissarov N Vlahakis A Konigl and M V BarkovldquoMagnetic acceleration of ultrarelativistic jets in gamma-rayburst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 394 no 3 pp 1182ndash1212 2009

[271] N Globus and A Levinson ldquoLoaded magnetohydrodynamicflows in Kerr spacetimerdquo Physical Review D vol 88 no 8Article ID 084046 2013

[272] N Globus and A Levinson ldquoJet formation in GRBs a semi-analytic model of MHD flow in Kerr geometry with realisticplasma injectionrdquo The Astrophysical Journal vol 796 no 1 p26 2014

[273] BDMetzgerDGiannios T AThompsonN Bucciantini andE Quataert ldquoThe protomagnetar model for gamma-ray burstsrdquoMonthly Notices of the Royal Astronomical Society vol 413 no3 pp 2031ndash2056 2011

[274] H C Spruit F Daigne and G Drenkhahn ldquoLarge scale mag-netic fields and their dissipation in GRB fireballsrdquo Astronomyand Astrophysics vol 369 no 2 pp 694ndash705 2001

[275] G Drenkhahn ldquoAcceleration of GRB outflows by Poynting fluxdissipationrdquo Astronomy amp Astrophysics vol 387 no 2 pp 714ndash724 2002

[276] G Drenkhahn and H C Spruit ldquoEfficient acceleration andradiation in poynting flux powered GRB outflowsrdquo Astronomyamp Astrophysics vol 391 no 3 pp 1141ndash1153 2002

[277] N Vlahakis and A Konigl ldquoRelativistic magnetohydrodynam-ics with application to gamma-ray burst outflows I Theoryand semianalytic trans-alfvenic solutionsrdquo The AstrophysicalJournal vol 596 no 2 pp 1080ndash1103 2003

[278] D Giannios ldquoSpectra of black-hole binaries in the lowhardstate from radio to X-raysrdquo Astronomy amp Astrophysics vol 437no 3 pp 1007ndash1015 2005

[279] D Giannios ldquoPrompt emission spectra from the photosphere ofa GRBrdquo Astronomy amp Astrophysics vol 457 no 3 pp 763ndash7702006

[280] D Giannios and H C Spruit ldquoSpectra of Poynting-flux pow-ered GRB outflowsrdquo Astronomy amp Astrophysics vol 430 no 1pp 1ndash7 2005

[281] P Meszaros and M J Rees ldquoGeV emission from collisionalmagnetized gamma-ray burstsrdquo Astrophysical Journal Lettersvol 733 no 2 article L40 2011

[282] F V Coroniti ldquoMagnetically striped relativistic magnetohy-drodynamic winds the Crab Nebula revisitedrdquo AstrophysicalJournal vol 349 no 2 pp 538ndash545 1990

[283] A Lichnerowicz Relativistic Hydrodynamics and Magnetohy-drodynamics Benjamin 1967

[284] M Gedalin ldquoLinear waves in relativistic anisotropic magneto-hydrodynamicsrdquoPhysical ReviewE vol 47 no 6 pp 4354ndash43571993

[285] B Zhang and S Kobayashi ldquoGamma-ray burst early afterglowsreverse shock emission from an arbitrarily magnetized ejectardquoThe Astrophysical Journal vol 628 no 1 pp 315ndash334 2005

[286] P Mimica D Giannios and M A Aloy ldquoDeceleration ofarbitrarily magnetized GRB ejecta the complete evolutionrdquoAstronomy and Astrophysics vol 494 no 3 pp 879ndash890 2009

[287] P Mimica and M A Aloy ldquoOn the dynamic efficiency ofinternal shocks in magnetized relativistic outflowsrdquo Monthly

Notices of the Royal Astronomical Society vol 401 no 1 pp 525ndash532 2010

[288] H C Spruit and G D Drenkhahn ldquoMagnetically poweredprompt radiation and flow acceleration in Grbrdquo in Gamma-RayBursts in the Afterglow Era M Feroci F Frontera N Masettiand L Piro Eds vol 312 of Astronomical Society of the PacificConference Series p 357 2004

[289] D A Uzdensky and J C McKinney ldquoMagnetic reconnectionwith radiative cooling I Optically thin regimerdquo Physics ofPlasmas vol 18 no 4 Article ID 042105 2011

[290] J C McKinney and D A Uzdensky ldquoA reconnection switch totrigger gamma-ray burst jet dissipationrdquoMonthly Notices of theRoyal Astronomical Society vol 419 no 1 pp 573ndash607 2012

[291] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoBeaming and rapid variability of high-energy radiation fromrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 754 no 2 article L33 2012

[292] B Cerutti G R Werner D A Uzdensky and M C BegelmanldquoSimulations of particle acceleration beyond the classical syn-chrotron Burnoff limit in magnetic reconnection an explana-tion of the Crab flaresrdquo The Astrophysical Journal vol 770 no2 article 147 2013

[293] G R Werner D A Uzdensky B Cerutti K Nalewajko andM C Begelman ldquoThe extent of power-law energy spectra incollisionless relativisticmagnetic reconnection in pair plasmasrdquohttparxivorgabs14098262

[294] J Contopoulos ldquoA simple type of magnetically driven jets anastrophysical plasma gunrdquo The Astrophysical Journal vol 450no 2 pp 616ndash627 1995

[295] A Tchekhovskoy R Narayan and J C McKinney ldquoMagne-tohydrodynamic simulations of gamma-ray burst jets beyondthe progenitor starrdquo New Astronomy vol 15 no 8 pp 749ndash7542010

[296] S S Komissarov N Vlahakis and A Konigl ldquoRarefactionacceleration of ultrarelativistic magnetized jets in gamma-ray burst sourcesrdquo Monthly Notices of the Royal AstronomicalSociety vol 407 no 1 pp 17ndash28 2010

[297] J Granot S S Komissarov and A Spitkovsky ldquoImpulsiveacceleration of strongly magnetized relativistic flowsrdquo MonthlyNotices of the Royal Astronomical Society vol 411 no 2 pp1323ndash1353 2011

[298] M Lyutikov ldquoThe electromagneticmodel of gamma-ray burstsrdquoThe New Journal of Physics vol 8 article 119 2006

[299] E Fermi ldquoOn the origin of the cosmic radiationrdquo PhysicalReview vol 75 no 8 pp 1169ndash1174 1949

[300] E Fermi ldquoGalactic magnetic fields and the origin of cosmicradiationrdquoThe Astrophysical Journal vol 119 p 1 1954

[301] M S Longair High Energy Astrophysics Cambridge UniversityPress Cambridge UK 2011

[302] A R Bell ldquoThe acceleration of cosmic rays in shock fronts IrdquoMonthly Notices of the Royal Astronomical Society vol 182 pp147ndash156 1978

[303] R D Blandford and J P Ostriker ldquoParticle acceleration byastrophysical shocksrdquoTheAstrophysical Journal vol 221 pp 29ndash32 1978

[304] R Blandford and D Eichler ldquoParticle acceleration at astrophys-ical shocks a theory of cosmic ray originrdquo Physics Reports vol154 no 1 pp 1ndash75 1987

[305] F C Jones and D C Ellison ldquoThe plasma physics of shockaccelerationrdquo Space Science Reviews vol 58 no 1 pp 259ndash3461991

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in Condensed Matter Physics

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Superconductivity

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Statistical MechanicsInternational Journal of

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AstrophysicsJournal of

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 Computational  Methods in Physics

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Soft MatterJournal of

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PhotonicsJournal of

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ThermodynamicsJournal of

34 Advances in Astronomy

[306] J G Kirk F M Rieger and A Mastichiadis ldquoParticle acceler-ation and synchrotron emission in blazar jetsrdquo Astronomy andAstrophysics vol 333 no 2 pp 452ndash458 1998

[307] J G Kirk A W Guthmann Y A Gallant and A AchterbergldquoParticle acceleration at ultrarelativistic shocks an eigenfunc-tion methodrdquoTheAstrophysical Journal vol 542 no 1 pp 235ndash242 2000

[308] D C Ellison S P Reynolds and F C Jones ldquoFirst-order Fermiparticle acceleration by relativistic shocksrdquo The AstrophysicalJournal vol 360 no 2 pp 702ndash714 1990

[309] A Achterberg Y A Gallant J G Kirk and A W GuthmannldquoParticle acceleration by ultrarelativistic shocks theory andsimulationsrdquoMonthly Notices of the Royal Astronomical Societyvol 328 no 2 pp 393ndash408 2001

[310] D C Ellison and G P Double ldquoDiffusive shock accelerationin unmodified relativistic oblique shocksrdquoAstroparticle Physicsvol 22 no 3-4 pp 323ndash338 2004

[311] L O Silva R A Fonseca J W Tonge J M Dawson W BMori and M V Medvedev ldquoInterpenetrating plasma shellsnear-equipartition magnetic field generation and nonthermalparticle accelerationrdquoTheAstrophysical Journal Letters vol 596no 1 pp L121ndashL124 2003

[312] K-I Nishikawa P Hardee G Richardson R Preece H Soland G J Flshman ldquoParticle acceleration in relativistic jets dueto Weibel instabilityrdquo The Astrophysical Journal vol 595 no 1pp 555ndash563 2003

[313] A Spitkovsky ldquoParticle acceleration in relativistic collisionlessshocks fermi process at lastrdquoThe Astrophysical Journal Lettersvol 682 no 1 pp L5ndashL8 2008

[314] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless pair shocks dependence of shockacceleration on magnetic obliquityrdquo The Astrophysical Journalvol 698 no 2 pp 1523ndash1549 2009

[315] T Haugboslashlle ldquoThree-dimensional modeling of relativistic colli-sionless ion-electron shocksrdquoTheAstrophysical Journal vol 739no 2 p L42 2011

[316] M M Romanova and R V E Lovelace ldquoMagnetic fieldreconnection and particle acceleration in extragalactic jetsrdquoAstronomy and Astrophysics vol 262 pp 26ndash36 1992

[317] S Zenitani and M Hoshino ldquoThe generation of nonthermalparticles in the relativistic magnetic reconnection of pairplasmasrdquo The Astrophysical Journal vol 562 no 1 pp 63ndash662001

[318] M Lyutikov ldquoRole of reconnection in AGN jetsrdquo New Astron-omy Reviews vol 47 no 6-7 pp 513ndash515 2003

[319] C H Jaroschek R A Treumann H Lesch and M ScholerldquoFast reconnection in relativistic pair plasmas analysis ofparticle acceleration in self-consistent full particle simulationsrdquoPhysics of Plasmas vol 11 no 3 pp 1151ndash1163 2004

[320] Y E Lyubarsky ldquoOn the relativistic magnetic reconnectionrdquoMonthly Notices of the Royal Astronomical Society vol 358 no1 pp 113ndash119 2005

[321] S Zenitani and M Hoshino ldquoParticle acceleration and mag-netic dissipation in relativistic current sheet of pair plasmasrdquoThe Astrophysical Journal vol 670 no 1 pp 702ndash726 2007

[322] S Zenitani and M Hoshino ldquoThe role of the guide field inrelativistic pair plasma reconnectionrdquoTheAstrophysical Journalvol 677 no 1 pp 530ndash544 2008

[323] Y Lyubarsky andM Liverts ldquoParticle acceleration in the drivenrelativistic reconnectionrdquo The Astrophysical Journal vol 682no 2 pp 1436ndash1442 2008

[324] L YinWDaughtonH Karimabadi B J Albright K J Bowersand J Margulies ldquoThree-dimensional dynamics of collisionlessmagnetic reconnection in Large-Scale pair plasmasrdquo PhysicalReview Letters vol 101 no 12 Article ID 125001 2008

[325] D Giannios ldquoUHECRs from magnetic reconnection in rela-tivistic jetsrdquo Monthly Notices of the Royal Astronomical SocietyLetters vol 408 no 1 pp L46ndashL50 2010

[326] A Lazarian G Kowal E Vishniac and E D G dal Pino ldquoFastmagnetic reconnection and energetic particle accelerationrdquoPlanetary and Space Science vol 59 no 7 pp 537ndash546 2011

[327] W Liu H Li L Yin B J Albright K J Bowers and E PLiang ldquoParticle energization in 3D magnetic reconnection ofrelativistic pair plasmasrdquo Physics of Plasmas vol 18 no 5Article ID 052105 2011

[328] N Bessho and A Bhattacharjee ldquoFast magnetic reconnectionand particle acceleration in relativistic low-density electron-positron plasmaswithout guide fieldrdquoTheAstrophysical Journalvol 750 no 2 article 129 2012

[329] D Kagan MMilosavljevic and A Spitkovsky ldquoA flux rope net-work and particle acceleration in three-dimensional relativisticmagnetic reconnectionrdquoThe Astrophysical Journal vol 774 no1 article 41 2013

[330] L Sironi and A Spitkovsky ldquoRelativistic reconnection anefficient source of non-thermal particlesrdquo The AstrophysicalJournal Letters vol 783 no 1 article L21 2014

[331] D A Uzdensky and A Spitkovsky ldquoPhysical conditions in thereconnection layer in pulsarmagnetospheresrdquoTheAstrophysicalJournal vol 780 no 1 p 3 2014

[332] L Sironi and A Spitkovsky ldquoParticle acceleration in relativisticmagnetized collisionless electron-ion shocksrdquoTheAstrophysicalJournal vol 726 no 2 2011

[333] R V E Lovelace ldquoDynamo model of double radio sourcesrdquoNature vol 262 no 5570 pp 649ndash652 1976

[334] R D Blandford ldquoAccretion disc electrodynamicsmdasha model fordouble radio sourcesrdquoMonthlyNotices of the RoyalAstronomicalSociety vol 176 no 3 pp 465ndash481 1976

[335] ANeronovDV Semikoz and I I Tkachev ldquoUltra-high energycosmic ray production in the polar cap regions of black holemagnetospheresrdquo New Journal of Physics vol 11 Article ID065015 2009

[336] C D Dermer J A Miller and H Li ldquoStochastic particleacceleration near accreting black holerdquo Astrophysical JournalLetters vol 456 no 1 pp 106ndash118 1996

[337] TW Jones and P E Hardee ldquoMaxwellian synchrotron sourcesrdquoThe Astrophysical Journal vol 228 pp 268ndash278 1979

[338] D F Cioffi and T W Jones ldquoInternal Faraday rotation effectsin transparent synchrotron sourcesrdquoThe Astronomical Journalvol 85 pp 368ndash375 1980

[339] G Wardzinski and A A Zdziarski ldquoThermal synchrotronradiation and its comptonization in compact X-ray sourcesrdquoMonthly Notices of the Royal Astronomical Society vol 314 no1 pp 183ndash198 2000

[340] A Persquoer and P Casella ldquoA model for emission from jets in X-ray binaries consequences of a single acceleration episoderdquoTheAstrophysical Journal vol 699 no 2 pp 1919ndash1937 2009

[341] R D Blandford and C F McKee ldquoRadiation from relativisticblast waves in quasars and active galactic nucleirdquo MonthlyNotices of the Royal Astronomical Society vol 180 no 3 pp 343ndash371 1977

[342] V L Ginzburg and S I Syrovatskii ldquoCosmic magneto-bremsstrahlung (synchrotron radiation)rdquo Annual Review ofAstronomy and Astrophysics vol 3 p 297 1965

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

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AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

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Statistical MechanicsInternational Journal of

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GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

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Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

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AerodynamicsJournal of

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PhotonicsJournal of

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Journal of

Biophysics

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ThermodynamicsJournal of

Advances in Astronomy 35

[343] G R Blumenthal and R J Gould ldquoBremsstrahlung syn-chrotron radiation and compton scattering of high-energyelectrons traversing dilute gasesrdquo Reviews of Modern Physicsvol 42 no 2 pp 237ndash271 1970

[344] M J Rees and P Meszaros ldquoRelativistic fireballsmdashenergyconversion and time-scalesrdquo Monthly Notices of the RoyalAstronomical Society vol 258 pp 41ndash43 1992

[345] P Meszaros and M J Rees ldquoRelativistic fireballs and theirimpact on externalmatter models for cosmological gamma-rayburstsrdquo Astrophysical Journal vol 405 no 1 pp 278ndash284 1993

[346] P Meszaros M J Rees and H Papathanassiou ldquoSpectralproperties of blast-wave models of gamma-ray burst sourcesrdquoThe Astrophysical Journal vol 432 no 1 pp 181ndash193 1994

[347] H Papathanassiou and P Meszaros ldquoSpectra of unsteady windmodels of gamma-ray burstsrdquo The Astrophysical Journal vol471 no 2 pp L91ndashL94 1996

[348] R Sari and T Piran ldquoCosmological gamma-ray bursts internalversus external shocksrdquoMonthly Notices of the Royal Astronom-ical Society vol 287 no 1 pp 110ndash116 1997

[349] R P Pilla and A Loeb ldquoEmission spectra from internal shocksin gamma-ray burst sourcesrdquo The Astrophysical Journal vol494 no 2 pp L167ndashL171 1998

[350] E S Weibel ldquoSpontaneously growing transverse waves in aplasma due to an anisotropic velocity distributionrdquo PhysicalReview Letters vol 2 no 3 pp 83ndash84 1959

[351] J T Frederiksen C B Hededal T Hauoboslashlle and A NordlundldquoMagnetic field generation in collisionless shocks patterngrowth and transportrdquo Astrophysical Journal Letters vol 608no 1 pp L13ndashL16 2004

[352] K-I Nishikawa P Hardee G Richardson R Preece HSol and G J Fishman ldquoParticle acceleration and magneticfield generation in electron-positron relativistic shocksrdquo TheAstrophysical Journal vol 622 no 2 pp 927ndash937 2005

[353] A Spitkovsky ldquoOn the structure of relativistic collisionlessshocks in electron-ion plasmasrdquo The Astrophysical JournalLetters vol 673 no 1 pp L39ndashL42 2008

[354] R A M J Wijers M J Rees and P Meszaros ldquoShocked byGRB 970228 the afterglow of a cosmological fireballrdquoMonthlyNotices of the Royal Astronomical Society vol 288 no 4 pp L51ndashL56 1997

[355] A Panaitescu and P Kumar ldquoProperties of relativistic jets ingamma-ray burst afterglowsrdquoTheAstrophysical Journal vol 571no 2 pp 779ndash789 2002

[356] R Santana R Barniol Duran and P Kumar ldquoMagnetic fields inrelativistic collisionless shocksrdquo Astrophysical Journal vol 785no 1 article 29 2014

[357] R Barniol Duran ldquoConstraining the magnetic field in GRB rel-ativistic collisionless shocks using radio datardquo Monthly Noticesof the Royal Astronomical Society vol 442 pp 3147ndash3154 2014

[358] R Sari R Narayan and T Piran ldquoCooling timescales andtemporal structure of gamma-ray burstsrdquo The AstrophysicalJournal vol 473 no 1 pp 204ndash218 1996

[359] R Sari T Piran and R Narayan ldquoSpectra and light curves ofgamma-ray burst afterglowsrdquoThe Astrophysical Journal Lettersvol 497 no 1 pp L17ndashL20 1998

[360] P Kumar and E McMahon ldquoA general scheme for modelling120574-ray burst prompt emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 384 no 1 pp 33ndash63 2008

[361] P Beniamini and T Piran ldquoConstraints on the synchrotronemission mechanism in gamma-ray burstsrdquo The AstrophysicalJournal vol 769 no 1 article 69 2013

[362] G Ghisellini A Celotti and D Lazzati ldquoConstraints on theemissionmechanisms of gamma-ray burstsrdquoMonthly Notices ofthe Royal Astronomical Society vol 313 no 1 pp L1ndashL5 2000

[363] A Persquoer and B Zhang ldquoSynchrotron emission in small-scalemagnetic fields as a possible explanation for prompt emissionspectra of gamma-ray burstsrdquo The Astrophysical Journal vol653 no 1 I pp 454ndash461 2006

[364] X Zhao Z Li X Liu B-b Zhang J Bai and P MeszarosldquoGamma-ray burst spectrumwith decayingmagnetic fieldrdquoTheAstrophysical Journal vol 780 no 1 p 12 2014

[365] Z L UhmandB Zhang ldquoFast-cooling synchrotron radiation ina decayingmagnetic field and 120574-ray burst emissionmechanismrdquoNature Physics vol 10 no 5 pp 351ndash356 2014

[366] N M Lloyd and V Petrosian ldquoSynchrotron radiation as thesource of gamma-ray burst spectrardquo The Astrophysical Journalvol 543 no 2 pp 722ndash732 2000

[367] J Granot T Piran and R Sari ldquoThe synchrotron spectrum offast cooling electrons revisitedrdquo The Astrophysical Journal vol534 no 2 pp L163ndashL166 2000

[368] A Persquoer and E Waxman ldquoThe high-energy tail of GRB 941017comptonization of synchrotron self-absorbed photonsrdquo TheAstrophysical Journal Letters vol 603 no 1 pp L1ndashL4 2004

[369] A Panaitescu and P Meszaros ldquoGamma-ray bursts fromupscattered self-absorbed synchrotron emissionrdquo The Astro-physical Journal Letters vol 544 no 1 pp L17ndashL21 2000

[370] C D Dermer and M Bottcher ldquoFlash heating of circumstellarclouds by gamma-ray burstsrdquoThe Astrophysical Journal Lettersvol 534 no 2 pp L155ndashL158 2000

[371] B E Stern and J Poutanen ldquoGamma-ray bursts from syn-chrotron self-compton emissionrdquo Monthly Notices of the RoyalAstronomical Society vol 352 no 3 pp L35ndashL39 2004

[372] E V Derishev V V Kocharovsky and V V KocharovskyldquoPhysical parameters and emission mechanism in gamma-rayburstsrdquo Astronomy and Astrophysics vol 372 no 3 pp 1071ndash1077 2001

[373] T Piran R Sari andY-C Zou ldquoObservational limits on inverseCompton processes in gamma-ray burstsrdquo Monthly Notices ofthe Royal Astronomical Society vol 393 no 4 pp 1107ndash11132009

[374] E Nakar S Ando and R Sari ldquoKlein-Nishina effects onoptically thin synchrotron and synchrotron self-compton spec-trumrdquo Astrophysical Journal Letters vol 703 no 1 pp 675ndash6912009

[375] F Daigne Z Bosnjak and G Dubus ldquoReconciling observedgamma-ray burst prompt spectra with synchrotron radiationrdquoAstronomy and Astrophysics vol 526 article 110 2011

[376] R Barniol Duran Z Bosnjak and P Kumar ldquoInverse-Comptoncooling in Klein-Nishina regime and gamma-ray burst promptspectrumrdquo Monthly Notices of the Royal Astronomical Societyvol 424 no 4 pp 3192ndash3200 2012

[377] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand gamma-ray burstsrdquo Astrophysical Journal Letters vol 511no 2 pp L93ndashL96 1999

[378] G Ghisellini and A Celotti ldquoQuasi-thermal comptonizationand GRBsrdquo Astronomy and Astrophysics Supplement Series vol138 no 3 pp 527ndash528 1999

[379] K Asano and T Terasawa ldquoSlow heating model of gamma-rayburst photon spectrum and delayed emissionrdquoThe Astrophysi-cal Journal vol 705 no 2 pp 1714ndash1720 2009

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

36 Advances in Astronomy

[380] K Murase K Asano T Terasawa and P Meszros ldquoThe roleof stochastic acceleration in the prompt emission of gamma-ray bursts application to hadronic injectionrdquoThe AstrophysicalJournal vol 746 no 2 article 164 2012

[381] NM Lloyd-Ronning andV Petrosian ldquoInterpreting the behav-ior of time-resolved gamma-ray burst spectrardquo AstrophysicalJournal Letters vol 565 no 1 pp 182ndash194 2002

[382] M V Medvedev ldquoTheory of lsquojitterrsquo radiation from small-scalerandommagnetic fields and prompt emission from gamma-rayburst shocksrdquoTheAstrophysical Journal vol 540 no 2 pp 704ndash714 2000

[383] M Bottcher and C D Dermer ldquoHigh-energy gamma rays fromultra-high-energy cosmic-ray protons in gamma-ray burstsrdquoAstrophysical Journal Letters vol 499 no 2 pp L131ndashL134 1998

[384] T Totani ldquoTeV burst of gamma-ray bursts and ultra-high-energy cosmic raysrdquoThe Astrophysical Journal Letters vol 509no 2 pp L81ndashL84 1998

[385] N Gupta and B Zhang ldquoPrompt emission of high-energyphotons from gamma ray burstsrdquo Monthly Notices of the RoyalAstronomical Society vol 380 no 1 pp 78ndash92 2007

[386] K Asano S Inoue and P Meszros ldquoPrompt high-energy emis-sion from proton-dominated gamma-ray burstsrdquo AstrophysicalJournal Letters vol 699 no 2 pp 953ndash957 2009

[387] S Razzaque ldquoSynchrotron radiation from ultra-high energyprotons and the fermi observations of GRB 080916CrdquoTheOpenAstronomy Journal vol 3 no 1 pp 150ndash155 2010

[388] K Asano and P Meszaros ldquoDelayed onset of high-energyemissions in leptonic and hadronic models of gamma-rayburstsrdquo Astrophysical Journal vol 757 no 2 article 115 2012

[389] P Crumley and P Kumar ldquoHadronic models for Large AreaTelescope prompt emission observed in Fermi gamma-rayburstsrdquo Monthly Notices of the Royal Astronomical Society vol429 no 4 pp 3238ndash3251 2013

[390] M Milgrom and V Usov ldquoPossible association of ultra-high-energy cosmic-ray eventswith strong gamma-ray burstsrdquoAstro-physical Journal Letters vol 449 no 1 pp L37ndashL40 1995

[391] E Waxman ldquoCosmological gamma-ray bursts and the highestenergy cosmic raysrdquo Physical Review Letters vol 75 no 3 pp386ndash389 1995

[392] EWaxman and J Bahcall ldquoHigh energy neutrinos from cosmo-logical gamma-ray burst fireballsrdquo Physical Review Letters vol78 no 12 pp 2292ndash2295 1997

[393] E Waxman ldquoHigh-energy cosmic rays from gamma-ray burstsources a stronger caserdquoTheAstrophysical Journal vol 606 no2 pp 988ndash993 2004

[394] D Eichler and A Levinson ldquoA compact fireball model ofgamma-ray burstsrdquoTheAstrophysical Journal vol 529 no 1 pp146ndash150 2000

[395] F Daigne and R Mochkovitch ldquoThe expected thermal precur-sors of gamma-ray bursts in the internal shockmodelrdquoMonthlyNotices of the Royal Astronomical Society vol 336 no 4 pp1271ndash1280 2002

[396] M J Rees and P Meszaros ldquoDissipative photosphere models ofgamma-ray bursts and X-ray flashesrdquoTheAstrophysical Journalvol 628 no 2 pp 847ndash852 2005

[397] A Persquoer and E Waxman ldquoPrompt gamma-ray burst spectradetailed calculations and the effect of pair productionrdquo TheAstrophysical Journal vol 613 no 1 pp 448ndash459 2004

[398] A Persquoer P Meszaros and M J Rees ldquoPeak energy clusteringand efficiency in compact objectsrdquo The Astrophysical Journalvol 635 no 1 pp 476ndash480 2005

[399] A Persquoer P Meszaros and M J Rees ldquoThe observable effects ofa photospheric component on GRB and XRF prompt emissionspectrumrdquo The Astrophysical Journal vol 642 no 2 pp 995ndash1003 2006

[400] B Zhang R-J Lu E-W Liang and X-F Wu ldquoGRB 110721Aphotosphere lsquodeath linersquo and the physical origin of the GRBBand functionrdquoTheAstrophysical Journal vol 758 no 2 articleL34 2012

[401] P Veres B-B Zhang and P Meszaros ldquoThe extremely highpeak energy of GRB 110721A in the context of a dissipativephotosphere synchrotron emission modelrdquo The AstrophysicalJournal Letters vol 761 no 2 article L18 2012

[402] D Giannios ldquoPrompt GRB emission from gradual energydissipationrdquo Astronomy and Astrophysics vol 480 no 2 pp305ndash312 2008

[403] D Giannios ldquoThe peak energy of dissipative gamma-ray burstphotospheresrdquo Monthly Notices of the Royal Astronomical Soci-ety vol 422 no 4 pp 3092ndash3098 2012

[404] P Veres and P Meszaros ldquoSingle- and two-component gamma-ray burst spectra in the Fermi GBM-LAT energy rangerdquo TheAstrophysical Journal vol 755 no 1 article 12 2012

[405] D Begue and A Persquoer ldquoPoynting flux dominated jets challengedby their photospheric emissionrdquoThe Astrophysical Journal vol802 no 2 article 134 2015

[406] H Gao and B Zhang ldquoPhotosphere emission from a hybridrelativistic outflow with arbitrary dimensionless entropy andmagnetization in GRBsrdquoThe Astrophysical Journal vol 801 no2 article 103 2015

[407] K Ioka K Murase K Toma S Nagataki and T NakamuraldquoUnstable GRB photospheres and eplusmn annihilation linesrdquo Astro-physical Journal vol 670 no 2 pp L77ndashL80 2007

[408] C Thompson P Meszaros and M J Rees ldquoThermalizationin relativistic outflows and the correlation between spectralhardness and apparent luminosity in gamma-ray burstsrdquo TheAstrophysical Journal vol 666 no 2 pp 1012ndash1023 2007

[409] D Lazzati B J Morsony and M C Begelman ldquoVery highefficiency photospheric emission in long-duration 120574-ray burstsrdquoThe Astrophysical Journal vol 700 no 1 pp 47ndash50 2009

[410] D Lazzati and M C Begelman ldquoNon-thermal emissionfrom the photospheres of gamma-ray burst outflows I High-frequency tailsrdquo The Astrophysical Journal vol 725 no 1 pp1137ndash1145 2010

[411] A Mizuta S Nagataki and J Aoi ldquoThermal radiation fromgamma-ray burst jetsrdquo The Astrophysical Journal vol 732 no1 article 26 2011

[412] D Lazzati B J Morsony andM C Begelman ldquoHigh-efficiencyphotospheric emission of long-duration gamma-ray burst jetsthe effect of the viewing anglerdquo The Astrophysical Journal vol732 no 1 article 34 2011

[413] K Toma X-F Wu and P Meszaros ldquoPhotosphere-internalshock model of gamma-ray bursts case studies of FermiLATburstsrdquo Monthly Notices of the Royal Astronomical Society vol415 no 2 pp 1663ndash1680 2011

[414] O Bromberg Z Mikolitzky and A Levinson ldquoSub-photo-spheric emission from relativistic radiation mediated shocks inGRBsrdquoThe Astrophysical Journal vol 733 no 2 p 85 2011

[415] A Levinson ldquoObservational signatures of sub-photosphericradiation-mediated shocks in the prompt phase of gamma-rayburstsrdquo The Astrophysical Journal vol 756 no 2 article 1742012

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Advances in Astronomy 37

[416] I Vurm Y Lyubarsky and T Piran ldquoOn thermalization ingamma-ray burst jets and the peak energies of photosphericspectrardquo The Astrophysical Journal vol 764 no 2 article 1432013

[417] AM Beloborodov ldquoRegulation of the spectral peak in gamma-ray burstsrdquoTheAstrophysical Journal vol 764 no 2 p 157 2013

[418] R Hascoet F Daigne and R Mochkovitch ldquoPrompt thermalemission in gamma-ray burstsrdquo Astronomy and Astrophysicsvol 551 article A124 2013

[419] D Lazzati B J Morsony R Margutti and M C BegelmanldquoPhotospheric emission as the dominant radiation mechanismin long-duration gamma-ray burstsrdquoThe Astrophysical Journalvol 765 no 2 article 103 2013

[420] K Asano and P Meszaros ldquoPhoton and neutrino spectra oftime-dependent photospheric models of gamma-ray burstsrdquoJournal of Cosmology and Astroparticle Physics vol 2013 no 9article 8 2013

[421] C Cuesta-Martinez M A Aloy P Mimica C Thone and Ade Ugarte Postigo ldquoNumerical models of blackbody-dominatedgamma-ray bursts II Emission propertiesrdquo Monthly Notices ofthe Royal Astronomical Society vol 446 no 2 pp 1737ndash17492015

[422] A Chhotray and D Lazzati ldquoGamma-ray burst spectra andspectral correlations from subphotospheric ComptonizationrdquoThe Astrophysical Journal vol 802 no 2 article 132 2015

[423] S Keren and A Levinson ldquoSub-photospheric radiation-mediated shocks in gamma-ray bursts multiple shock emissionand the band spectrumrdquoThe Astrophysical Journal vol 789 no2 p 128 2014

[424] R Ruffini I A Siutsou and G V Vereshchagin ldquoA theory ofphotospheric emission from relativistic outflowsrdquo The Astro-physical Journal vol 772 no 1 article 11 2013

[425] A G Aksenov R Ruffini and G V Vereshchagin ldquoComp-tonization of photons near the photosphere of relativisticoutflowsrdquoMonthlyNotices of the Royal Astronomical Society vol436 no 1 pp L54ndashL58 2013

[426] G V Vereshchagin ldquoPhysics of nondissipative ultrarelativisticphotospheresrdquo International Journal of Modern Physics DGravitation Astrophysics Cosmology vol 23 no 3 Article ID1430003 2014

[427] W Zhang S E Woosley and A I MacFadyen ldquoRelativistic jetsin collapsarsrdquoTheAstrophysical Journal vol 586 no 1 pp 356ndash371 2003

[428] A Persquoer and E Waxman ldquoTime-dependent numerical modelfor the emission of radiation from relativistic plasmardquo TheAstrophysical Journal vol 628 no 2 pp 857ndash866 2005

[429] C Lundman A Persquoer and F Ryde ldquoPolarization properties ofphotospheric emission from relativistic collimated outflowsrdquoMonthly Notices of the Royal Astronomical Society vol 440 no4 pp 3292ndash3308 2013

[430] Z Chang H-N Lin and Y Jiang ldquoGamma-ray burst polariza-tion via compton scattering processrdquoThe Astrophysical Journalvol 783 no 1 p 30 2014

[431] H Ito S Nagataki M Ono et al ldquoPhotospheric emission fromstratified jetsrdquo The Astrophysical Journal vol 777 no 1 article62 2013

[432] A Persquoer F Ryde R A M J Wijers P Meszaros and M JRees ldquoA newmethod of determining the initial size and Lorentzfactor of gamma-ray burst fireballs using a thermal emissioncomponentrdquoThe Astrophysical Journal vol 664 no 1 2007

[433] J Larsson J L Racusin and J M Burgess ldquoEvidence for jetlaunching close to the black hole inGRB 101219Bmdasha FermiGRBdominated by thermal emissionrdquoTheAstrophysical Journal vol800 no 2 article L34 2015

[434] A Mizuta and K Ioka ldquoOpening angles of collapsar JETSrdquoTheAstrophysical Journal vol 777 no 2 article 162 2013

[435] B Zhang and P Meszaros ldquoAn analysis of gamma-ray burstspectral break modelsrdquo The Astrophysical Journal vol 581 no2 pp 1236ndash1247 2002

[436] B Zhang and A Persquoer ldquoEvidence of an initially magneticallydominated outflow in GRB 080916CrdquoTheAstrophysical JournalLetters vol 700 no 2 pp L65ndashL68 2009

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FluidsJournal of

Atomic and Molecular Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in Condensed Matter Physics

OpticsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstronomyAdvances in

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Superconductivity

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Statistical MechanicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GravityJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AstrophysicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Physics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Solid State PhysicsJournal of

 Computational  Methods in Physics

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

PhotonicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Biophysics

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ThermodynamicsJournal of