Download - Gamma Ray Bursts João Braga - INPE
Gamma Ray BurstsGamma Ray Bursts João Braga - INPE
Dark ages of GRBs BATSE/CGRO: some light GRBs x SGRs, magnetars BeppoSAX: afterglows and IDs Progenitors Host galaxies and cosmology HETE, SWIFT and the future
Dark AgesDark Ages
July 1967: Vela satellites detect gamma ray outbursts
16 peculiar events of cosmic origin short (~s) photon flashes with E > 100 MeV publication only in 1973
Dark AgesDark Ages
After ~30 ys
only a reasonable idea of what they are
Phenomenology of bursts in the DAs:
almost no association with known objects statistically poor distribution
no clue
Dark AgesDark Ages
Burst of March 5th, 1979
SNR N49 in LMC (~10,000 ys) 8 s oscillations in ~200 s
Nature of GRBs associated with Galactic neutron stars: rapid variability compact object (light-seconds) cyclotron lines @ tens of keV B ~ 1012 G : = eB/mc emission lines @ hundreds of KeV redshifted 511 keV
zobs = z0 (1 – 2GM/c2 R)
periodicity rotation of a NS : R3 < (GM/42) T2
BATSE – COMPTON GROBATSE – COMPTON GRO• ~3000 bursts (~1 each day)• Isotropic distribution
- No concentration towards LMC, M31 or nearby clusters
- No dipole and quadupole moments• No spectral lines• No periodicity
Hundreds of models proposed
BATSE – COMPTON GROBATSE – COMPTON GRO• Bimodal distribution
— most are longer than 2 s— ~1/3 are shorter than 2 s
• Spectra: combination of two power-laws- spectrum softens with time
- Ep decreases with time (in the E.f(E) x E plot)
• Fluence: ~ 10-6 — 10-4 erg cm-2
long duration and hard spectrum bursts deviate more from a 3-D Euclidean brightness distribution
Euclidean
Soft Gamma Ray Repeaters Soft Gamma Ray Repeaters SGR SGR
Burst of March 9Burst of March 9thth, 1979, 1979
SNR N49 in LMC (~10,000 ys)
8 s oscillations in ~200 s
SOFT GAMMA RAY REPEATERSSOFT GAMMA RAY REPEATERS bursts repeat soft spectra (E 100 keV) short duration (~100 ms) Galactic “distribution”, associated with SNRs
Soft Gamma Ray Repeaters Soft Gamma Ray Repeaters SGR SGR
Soft Gamma Ray Repeaters Soft Gamma Ray Repeaters SGR SGR
Rotating magnetized Rotating magnetized neutron stars neutron stars
dE B2 R6 4 sin2 = dt 6 c3
Erot= I 2/2 ; P = 2 /
dE . = I dt . c 3/2 3IPP 1/2 B =B = RR33 sin sin 2 2
Rotating magnetized Rotating magnetized neutron stars neutron stars
for SGR 0525-66 (5/3/79):~1 ms 8 s in ~10 kys . P ~ 3 x 10-11 s s-1
B ~1015 G !!
MAGNETARMAGNETAR
Rotating magnetized Rotating magnetized neutron stars neutron stars
Very high fields
Fast spindown
SGRs are young NSs which should still be associated to
SNRs
MAGNETARSMAGNETARS
QuickTime Movie
MAGNETARSMAGNETARS
How do the bursts happen? NS crust brakes due to EM tensions (starquakes) Alfvén waves injected in the magnetosphere particle acceleration optically thick pair plasma forms gamma-ray emission
MAGNETARSMAGNETARS
Problems:
In 1900+14, RXTE measured a much . smaller P 2 ys before the 1998 active period
EB increased by more than 100%
Spindown is not magnetic and may be due
to relativistic winds (no magnetar!)
BeppoSAX and AfterglowsBeppoSAX and Afterglows
BeppoSAX:- 4 narrow field instruments(.1 to 300 keV; ~arcminute res.)- Wide Field Camera(2 to 25 keV; 200 x 200 ; 5’; coded-mask)- Gamma Ray Burst Monitor(60 to 600 keV; side shield)
BeppoSAX and AfterglowsBeppoSAX and Afterglows
97 Feb 28: GRB 970228 Discovered by GRBM and WFC NFIs observe 1SAX J0501.7+1146
First clear evidence of a GRB X-ray tail
Non-thermal spectra X-ray fluence is 40% of -ray fluence
BeppoSAX and AfterglowsBeppoSAX and Afterglows
BeppoSAX and RXTE discovered several other afterglows
Optical transients: Observed in appr. ½ of the well localized
bursts GRB 990123 is the only one observed in the
optical when the gamma-ray flash was still going on
GRB 990123GRB 990123
GRB 011121GRB 011121
GRB 011121GRB 011121
Host galaxiesHost galaxies Optical IDs distant galaxies (low luminosity, blue) ~20 measured redshifts All in the z = 0.3 – 4.5 range, with the
exception of GRB 980425, possibly associated with SN 1998bw @ z = 0.008
OT is never far from center
redshiftsredshifts
ProgenitorsProgenitors Long GRBs are probably associated with
massive and short-lived progenitorsmassive and short-lived progenitors
GRBs may be associated with rare types of supernovae
Hypernovae: colapse of rotating massive star black hole accreting from a toroid
Collapsar: coalescence with a compact companion GRBs and SN-type remnant
ProgenitorsProgenitors Short GRBs are probably associated with
mergers of compact objectsmergers of compact objects
The fireball modelThe fireball model Observed fluxes require 1054 erg emitted in
seconds in a small region (~km)
Relativistic expanding fireball (e± , )Problem: energy would be converted into Ek of
accelerated baryons, spectrum would be quasi-thermal, and events wouldn’t be much longer than ms.
Solution: fireball shock modelfireball shock model: shock waves will inevitably occur in the outflow (after fireball becomes transparent) reconvert Ek into
nonthermal particle and radiation energy.
The fireball modelThe fireball model Complex light curves are due to internal shocks
caused by velocity variations. Turbulent magnetic fields built up behind the
shocks synchrotron power-law radiation spectrum Compton scattering to GeV range.
Jetted fireballJetted fireball: fireball can be significantly collimated if progenitor is a massive star with rapid rotation escape route along the rotation axis jet formation alleviate energy requirements higher burst rates
High Energy Transient ExplorerHigh Energy Transient Explorer
First dedicated GRB mission, X- and -rays Equatorial orbit, antisolar pointing launched on Oct 9th, 2000 - Pegasus 3 instruments, 1.5 sr common FOV
SXC (0.5-10 keV) - < 30” localization
WXM (2 –25 keV) - < 10’ localization FREGATE (6-400keV) - sr localization Rapid dissemination ( 1s) of GRB positions
(Internet and GCN)
HETEHETE
HETE Investigator TeamHETE Investigator Team
UC BerkeleyUC BerkeleyKevin Hurley J. Garrett Jernigan
MITMITGeorge R. Ricker (PI) Geoffrey Crew John P.Doty Al Levine Roland Vanderspek Joel Villasenor
LANLLANLEdward E. Fenimore Mark Galassi
RIKENRIKENMasaru Matsuoka Nobuyuki Kawai Atsumasa Yoshida
CESRCESRJean-Luc Atteia Gilbert Vedrenne Jean-Francois Olive
Michel Boer
UChicagoUChicagoDonald Q. LambCarlo Graziani
INPEINPEJoão Braga
UC Santa CruzUC Santa CruzStanford Woosley
CNESCNESJean-Luc Issler
SUP’AEROSUP’AEROChristian Colongo
CNRCNRGraziella Pizzichini
TIRFTIRFRavi Manchanda
HETE in the PegasusHETE in the Pegasus
Ground station networkGround station network
GRB 010921GRB 010921 Bright (>80) burst detected on Sept 21, 2001
05:15:50.56 UT by FREGATE First HETE-discovered GRB with counterpart Detected by WXM, giving good X position (10o x 20’ strip) Cross-correlation with Ulysses time history
IPN annulus (radius 60o ± 0.118o)
intersection gives error region with 310 arcmin2 centered at
~ 22h55m30s, ~ 40052’
GRB 010921GRB 010921
GRB 010921GRB 010921 Highly symmetric at high
energies Lower S/N for WXM due to
offset Durations increase by 65% at
lower energies Hard-to-soft spectral evolution Peak energy flux in the 4-25
keV band is 1/3 of 50-300 keV Peak photon flux is ~4 times
higher in the 4-25 keV
DiscussionDiscussion Long duration GRB X-ray rich, but no XRF (high 50-300 keV flux) z = 0.450 isotropic energy of 7.8 x 1051 erg
(M=0.3, =0.7, H0=65 km s-1 Mpc-1) - less if
beamed Second lowest z strong candidate for extended
searches for possible associated supernova Final position available 15.2h after burst
ground-based observations in the first night counterpart established well within HETE-IPN error region
ConclusionsConclusions
GRBs occur at a rate of (no beaming)
a few/day/universe or 1/few million ys/average galaxy or ~10-91 cm-3 s-1
(since observed GRBs are detectable out to z ~10) New missions are very important
SWIFT: 3 instruments, 250-300 bursts/yr, coverage from optical to gamma-rays, arcsecond positions,
will detect bursts up to z ~20.INTEGRAL, EXIST, MIRAX
Cosmology: burts can proble early universe and some could be related to Pop III stars
metal enrichment and ionization of the primordial gas.