gamma-ray bursts

L. Piro - ILIAS meeting - 2008L. Piro - ILIAS meeting - 2008 11

Gamma-Ray Gamma-Ray BurstsBursts

Gamma-Ray Gamma-Ray BurstsBursts

Luigi PiroLuigi Piro

Istituto Istituto Astrofisica Astrofisica

Spaziale Fisica Spaziale Fisica CosmicaCosmica - -

RomaRoma

INAFINAF


SummarySummary

GRB: the breakthroughs of the last GRB: the breakthroughs of the last decadedecade

Main theoretical and observational Main theoretical and observational backgroundbackground

Clues to the progenitors Clues to the progenitors Open issuesOpen issuesCosmological PerspectivesCosmological Perspectives


BeppoSAX: GRB in the BeppoSAX: GRB in the afterglow Eraafterglow Era

Launch: Apr. 30, 1996 Launch: Apr. 30, 1996 End ops: April 30, 2002End ops: April 30, 2002Discovery of the afterglows Discovery of the afterglows

of GRBof GRBDiscovery of the Discovery of the

extragalactic distancesextragalactic distancesProgenitor: Association with Progenitor: Association with

SN and star formation in SN and star formation in distant galaxies distant galaxies

Dark GRB’s and X-ray flashesDark GRB’s and X-ray flashesCosmology with GRBCosmology with GRB


GRB970228: the 1st X-GRB970228: the 1st X-ray and O afterglowray and O afterglow

•A second pointing 3 days after the GRB: fading X-ray counterpart (Costa et al 1997)

• Optical fading source (van Paradijs

et al 1997)

•Fast follow up with NFI in 8 hrs: a bright unknown X-ray source


Internal vs external shock: Internal vs external shock: prompt & afterglow prompt & afterglow

emissionemission In contrast with the In contrast with the afterglow, the prompt afterglow, the prompt emission is emission is characterized by characterized by strong hard-to-soft strong hard-to-soft spectral evolution from spectral evolution from X- to Gamma rays X- to Gamma rays (e.g. (e.g. GRB960720 Piro et al 1997) GRB960720 Piro et al 1997)


The fireball modelThe fireball modelThe fireball modelThe fireball model

106 cm

t-1

1016 cm

1013 cm

taft

X-ray afterglow

RB

tGRB


Afterglow spectrum: fireball Afterglow spectrum: fireball modelmodel

Galama et al 98


GRB970508: direct evidence of GRB970508: direct evidence of fireballfireballDiscovery of the Discovery of the

radio afterglowradio afterglowDirect evidence of a Direct evidence of a

relativistic relativistic expanding source by expanding source by radio scintillation radio scintillation induced by electrons induced by electrons in the Galaxy ISM (3 in the Galaxy ISM (3 uarcsec)uarcsec)


The progenitors of GRBThe progenitors of GRB The progenitors of GRBThe progenitors of GRB

NS-NS (BH-NS & BH-WD) travel far from their formation sites before producing GRB’s (Fryer et al 2000) => “clean environment”

The nature of the progenitor can be inferred from the environment

NS- NS merging NS- NS merging Collapsar

• Hypernovae/collapsar evolve much faster, going off in their formation site => “mass-rich environment”


Progenitors and hostsProgenitors and hosts

Fryer, Woosley and Hartmann 1999Fryer, Woosley and Hartmann 1999


The fading OT of The fading OT of GRB990123GRB990123


Host galaxies of Host galaxies of long GRBs: long GRBs: Normal (spiral) Normal (spiral) showing star showing star formationformation

most GRB most GRB within the half-within the half-light radius of light radius of the galaxy: the galaxy: star-formation star-formation sites and sites and massive massive progenitorsprogenitors


X-ray absorption in the X-ray absorption in the GRB local environmentGRB local environment

X-ray absorption column densities in the X-ray absorption column densities in the afterglow: NH=10afterglow: NH=1021-22 21-22 cmcm-2-2 (Stratta et al 2000, Campana et (Stratta et al 2000, Campana et

al 2006) al 2006) Consistent with Giant molecular cloudsConsistent with Giant molecular clouds


GRB-SN connectionGRB-SN connection

GB980425: in the GB980425: in the BeppoSAX error BeppoSAX error boxbox:: SN1998bw SN1998bw (Pian et al. 99,Kulkarni et al, (Pian et al. 99,Kulkarni et al,

Galama et al al 98)Galama et al al 98).. Exploded within 1 Exploded within 1 day from the day from the GRB. Chance GRB. Chance P=1E-4P=1E-4


GRB-Sn: 030329GRB-Sn: 030329 Sn contribution should Sn contribution should

appear when the power-appear when the power-law GRB afterglow has law GRB afterglow has decreased (Bloom et al decreased (Bloom et al 98: GRB980326)98: GRB980326)

GRB030329: The GRB030329: The nearest (and the nearest (and the brightest in HETE2 brightest in HETE2 GRB) z=0.168 (Greiner GRB) z=0.168 (Greiner et al, VLT)et al, VLT)

SN spectrum (similar to SN spectrum (similar to 1998bw) emerging at 1998bw) emerging at about 10 days about 10 days (Matheson et al 03, (Matheson et al 03, Hjorth et al 03). Hjorth et al 03).


GRB (high )

XRF (low )

Sub energetic X-ray flashes

Woosley et al

Collapsar model


Jet vs spherical Jet vs spherical expansion: break in the expansion: break in the

afterglow light curveafterglow light curve

Jet vs spherical Jet vs spherical expansion: break in the expansion: break in the

afterglow light curveafterglow light curve

t1 t2 t3 t4 t5

F

tt4

Jet

Spher.

(t4)= The break must be achromaticThe break must be achromatic


Simultaneous O and X-Simultaneous O and X-ray light curves of ray light curves of

GB990510GB990510

Simultaneous O and X-Simultaneous O and X-ray light curves of ray light curves of

GB990510GB990510 Break in the O at t= 1day Break in the O at t= 1day (Harrison et al (Harrison et al

99)99)

BeppoSAX light curve BeppoSAX light curve compatible compatible with break with break ((Kuulkers et al 2000Kuulkers et al 2000, Pian et al01, Pian et al01) )

but not requiredbut not required (Piro et al.00) (Piro et al.00)

SWIFT data show a variety of SWIFT data show a variety of behaviour, achromatic breaks are a behaviour, achromatic breaks are a small fractionsmall fraction..

1 10

T-T0(days)


X-ray flashesX-ray flashesX-ray flashesX-ray flashes A New class A New class

discovered by BSAX discovered by BSAX and confirmed by and confirmed by HETE2: HETE2: about 40% about 40% GRB’s with no or very GRB’s with no or very faint or gamma-ray faint or gamma-ray emission emission

high redshift GRBs high redshift GRBs off-axis eventsoff-axis events Subenergetic events, Subenergetic events,

more numerous than more numerous than normal GRBs normal GRBs

Heise et al 2001


XRF host galaxiesXRF host galaxies2 of XRF localized by BSAX and 2 of XRF localized by BSAX and

followed up by Chandra, followed up by Chandra, more redshift by SWIFT at z<3 more redshift by SWIFT at z<3

(Gendre, Galli, LP, 2007)(Gendre, Galli, LP, 2007)

XRF

GRB


GRB seen off axis: GW trigger + orphan Opt/X-GRB seen off axis: GW trigger + orphan Opt/X-ray afterglowsray afterglows

GRB seen off axis: GW trigger + orphan Opt/X-GRB seen off axis: GW trigger + orphan Opt/X-ray afterglowsray afterglows

106 cm

t-1

1016 cm

1013 cm

RB

tGRBtaft

X-ray afterglow


Dark GRBsDark GRBs BeppoSAX showed that >90% GRB are BeppoSAX showed that >90% GRB are

followed by X-ray afterglows. Confirmed by followed by X-ray afterglows. Confirmed by SWIFT. However only about 40% have optical SWIFT. However only about 40% have optical afterglows. afterglows.

High z (z>5) events ?High z (z>5) events ?


Short GRB’sShort GRB’s Short GRB’sShort GRB’s About 25% of GRB’s have durations About 25% of GRB’s have durations

<1 sec,down to few msec.<1 sec,down to few msec. No No counterpart so far. Different counterpart so far. Different progenitorsprogenitors (NS-NS mergers) (NS-NS mergers)??

Paciesas et al 99

T90=40 ms

Gehrels et al 05

GRB050509B


Entering SWIFTEntering SWIFT


HOST GALAXIES OF HOST GALAXIES OF SHORT BURSTS: SHORT BURSTS:

Elliptical AND SpiralElliptical AND SpiralGRB050509 GRB050724GRB050709

GRB050813 GRB050906


Temporal evolution for Temporal evolution for mergersmergers

Fryer, Woosley and Hartmann 1999Fryer, Woosley and Hartmann 1999


Redshift distribution of long- Redshift distribution of long- & short-GRBs & short-GRBs

However, suggestions that at least 25% of short-GRBs are at z>0.7 (Berger et al. 2006) ( if they did not travel long distances from their HG)


X-ray light curves of X-ray light curves of SHBsSHBs


X-ray to prompt X-ray to prompt γγ-ray -ray fluencefluence

One explanation (but not unique): lower density in short GRBs


1) 1) ElectromagnElectromagnetic window:etic window:

Afterglow: Afterglow:

properties of properties of the the environment environment (host galaxy, (host galaxy, density,..)density,..)

SN featuresSN features Long: Yes Long: Yes

(outliers?)(outliers?) Short. NOShort. NO

2) 2) GravitatioGravitational waves nal waves by GRBs:by GRBs:

Binary Binary merger:merger:

a)a) in-spiralin-spiralb) merger,b) merger,c) ring down c) ring down For For

collapsars collapsars NO NO inspiralinspiral

THE GRB PROGENITORS THE GRB PROGENITORS

LONG=COLLAPSAR

SHORT=NS-NS mergers

The tell tale feature from GW


Time delay GW-GRBTime delay GW-GRB

Collapsar case (e.g. Waxman and Collapsar case (e.g. Waxman and Meszaros 2003):Meszaros 2003): the jet inside the star can be the jet inside the star can be

subrelativisticsubrelativisticThe jet stream needs to be maintained The jet stream needs to be maintained

for several tens of seconds to overcome for several tens of seconds to overcome the pressure inside the star (cork effect)the pressure inside the star (cork effect)

NS-NS mergersNS-NS mergersMuch shorter Much shorter


GRBs by VIRGO and GRBs by VIRGO and LIGOLIGObh-ns bh-ns mm11=12 M=12 M m m22 =1.4 M =1.4 M

- - - in-spiral - -merger ring-down

Collapsar mCollapsar m11= m= m22 =1 M =1 M

- - - - merger- - - - merger

Initial VirgoUpgraded Virgo

2300 Mpc

280 Mpc

62 Mpc

Upgraded VirgoVirgo

110 Mpc

27 Mpc 23 Mpc

GRB 980425 d=40 MpcGRB 980425 d=40 MpcGRB020618 D=130Mpc

GRB050709 D=650Mpc


1

0.5

Precursors, flares and Precursors, flares and central enginecentral engine

X-ray X-ray precursorprecursor

Hard prompt Hard prompt emissionemission

X-ray flare X-ray flare at 300 s with at 300 s with spectrum spectrum similar to similar to the late the late afterglowafterglow

Piro et al. 05, ApJ.


The canonical X-ray light curve after SWIFT

Prompt: IS

Prompt: IS, curvature emission

Flattening: refreshed shocks, off axis jet, ….

External shock (classical power law)

Jet break

X-ray flares


X-ray FlaresX-ray FlaresSWIFT: Burrows et al (2005)BeppoSAX: Piro et al (2005)

Signature of long duration activity of the central engine

SWIFT: about 40% X-ray afterglows showing X-ray flares on time scales >100 sec (Chincarini et al 2007)


GRB050904: z=6.3GRB050904: z=6.3

Kawai et al 2005Kawai et al 2005 SWIFT X-ray data (Cusumano et al, Campana et al., SWIFT X-ray data (Cusumano et al, Campana et al.,

Gendre et al)Gendre et al)

GRBs in the dark Universe


GRBs as cosmological GRBs as cosmological beaconsbeacons

measure the cosmic measure the cosmic history of metalshistory of metals in in GRB regionsGRB regions and and their host galaxies their host galaxies

pinpoint the pinpoint the formation of early formation of early population of population of luminous sources luminous sources ignited in the dark ignited in the dark Universe (z>7)Universe (z>7)

Solve the missing Solve the missing baryon problem baryon problem residing in the residing in the cosmic web filamentscosmic web filaments


ConclusionsConclusions Progenitors Progenitors

circumstantial evidence associating long events to Massive circumstantial evidence associating long events to Massive star (collapsar) and short events to mergers. star (collapsar) and short events to mergers.

GW can be crucialGW can be crucial Central engineCentral engine

Still to be really understood (BH+AD)Still to be really understood (BH+AD) X-ray flares (and their GeV counterparts with AGILE and X-ray flares (and their GeV counterparts with AGILE and

GLAST) as evidence of long duration engine (fragmented AD)GLAST) as evidence of long duration engine (fragmented AD) Fireball modelFireball model

General agreement, but too simplistic:General agreement, but too simplistic: Jet breaks not so common as expected Jet breaks not so common as expected X-ray and optical appear to be decoupled X-ray and optical appear to be decoupled

Cosmological PerspectivesCosmological Perspectives GRB can probe throughout the Universe from present era to GRB can probe throughout the Universe from present era to

dark ages dark ages


Conclusions for GWConclusions for GW

GW provide direct information on the central GW provide direct information on the central engineengine

Good prospect of detections from nearby GRB Good prospect of detections from nearby GRB with advanced LIGO/VIRGO using EM triggerwith advanced LIGO/VIRGO using EM trigger

Rate should be 100 times larger than EM Rate should be 100 times larger than EM burst, due to collimation (EM counterpart: burst, due to collimation (EM counterpart: XRF and Orphan afterglows)XRF and Orphan afterglows)

In the future GW could provide the trigger In the future GW could provide the trigger and coarse (1 deg position) to carry out fast and coarse (1 deg position) to carry out fast follow up observations in X-rays with mission follow up observations in X-rays with mission like EDGE to detect the orphan afterglows of like EDGE to detect the orphan afterglows of GRB jets pointing away from earth GRB jets pointing away from earth

gamma-ray bursts

Documents

grb960720 piro et

greiner et

campana et

kulkarni et

bloom et

hjorth et

stratta et

galama et