GRB Useful reviews: Waxman astro-ph/0103186 Ghisellini astro-ph/0111584 Piran astro-ph/0405503 Meszaros astro-ph/0605208 Gehrels 2009 ariv:0909.1531 Useful links: http://qso.lanl.gov/~clf/papers (Chris Fryer lectures) Theory and observations
GRBs most luminous objects in the Universe!! • Sun Luminosity L~4 1033 erg/s • Supernova L~1051 erg/s • Galaxies with nuclei L~1048 erg/s • GRB luminosity L~1052 erg/s
GRBs: flashes of 0.1 MeV gamma rays that last 1-100 s 0.2 s short 20 s long • Duration: T90 Most show t ~ 64 ms Some t ~ 1 ms • Variability: -ray observationssummary • Isotropy in the sky • Flux: f = 10-4 -10-7 erg/cm2 s • Rate R 300/yr BATSE and 100/yr Swift
GRB 3 July 1969: first detection of a GRB by Vela 5A
Vela Satellites • 105 km Orbits • Launched in pairs – launched 1963-1965 • Operated until 1979 • All satellites allowed for some localization.
Vela Satellites - Results • 73 Bursts in Gamma-Rays over 10 years • Not from the Earth (not weapons tests) and not in the plane of solar system Ray Klebasadel
Gamma-Ray Bursts in the Solar System • Lightning in the Earth’s atmosphere (High Altitude) • Relativistic Iron Dust Grains • Magnetic Reconnection in the Heliopause Red Sprite Lightning
Gamma-Ray Bursts in the Milky Way • Accretion Onto White Dwarfs • Accretion onto neutron stars I) From binary companion II) Comets • Neutron Star Quakes • Magnetic Reconnection X-ray Novae
Galactic Gamma-Ray Bursts: Soft Gamma-Ray Repeaters • One Class of GRBs • Is definitely Galactic: • Soft gamma-ray • Repeaters (SGRs) • Characteristics: • Repeat Flashes • Photon Energy • Distribution lower • Energy than other • GRBs (hard x-rays) X-ray map of N49 SN remnant. The white Box shows location of the March 5th event
Models for SGRs • Accretion I) Binary Companion - no companion seen II) SN Fallback – Too long after explosion • Magnetic Fields ~1015 G Fields -“Magnetars”
Extragalactic Models • Large distances means large energy requirement (1051erg) • Event rate rare (10-6-10-5 per year in an L* galaxy) – Object can be exotic
Cosmological Models • Collapsing WDs • Stars Accreting on AGN • White Holes • Cosmic Strings • Black Hole Accretion Disks I) Binary Mergers II) Collapsing Stars
Black-Hole Accretion Disk (BHAD) Models Binary merger or Collapse of rotating Star produces Rapidly accreting Disk (>0.1 solar Mass per second!) Around black hole.
Massive Star Collapse Stan Woosley Collapsar Model – Collapse of a Rotating Massive Star into a Black Hole Main Predictions: Beamed Explosion, Accompanying supernova-like explosion
BATSE - Burst And Transient Spectrometer Experiment BATSE Module BATSE Consists of two NaI(TI) Scintillation Detectors: Large Area Detector (LAD) For sensitivity and the Spectroscopy Detector (SD) for energy coverage 8 Detectors Almost Full Sky Coverage Few Degree Resolution 20-600keV
Gamma-Ray Burst Lightcurves GRB990316 GRB Lightcurves have A broad range of Characteristics Fast Rise Exponential Decay “FREDs” GRB970508
Gamma-Ray Burst Durations Two Populations: Short – 0.03-3s Long – 3-1000s Possible third Population 1-10s
BATSE - Summary • GRBs are Isotropic – The beginning of the end for Galactic Models, but persistent theorists move the Galactic Models to the Halo • GRBs come in all shapes and sizes but two obvious subgroups exist - I) Short, Hard Bursts II) Long, Soft Bursts
BeppoSAX Italian-Dutch Satellite Launch: April 30, 1996 Goal: Positional Accuracy <5 arc minutes Honoring Giuseppe Occhialini
High Pressure Gas Scintillation Proportional Counter WFC – 40o x 40o, 2-28keV
Xenon Gas Scintillator Energy Range: .1-1keV (1-10keV) ~1 arc minute resolution Goal – Localize Object HPGSPC - High Pressure Xenon/He Gas PDS Phoswitch - NaI(Tl), CsI(Na) Scintillators 4-120keV (15-300keV) Goal – Broad Energy resolution in X-ray narrow field BeppoSAX Instruments LECS/MECS HPGSPC PDS
BeppoSAX: I GRB sono sorgenti a distanze cosmologiche! Costa+ 1997 BeppoSAX Pedichini+ 1997 Campo imperatore Van Paradijs+ 1997 WHT
GRB 970228 – host galaxy observed? This blob, a peculiar Galaxy to be sure, Is in the same position As the Burst! Could it have been the GRBs host? The galaxy has a Redshift of 0.695.
GRB 970508 – Optical Counterpart BeppoSAX X-ray Localization Allowed a The Optical Transient to Be detected While still on The rise. OT allowed Spectral Measurement!
flux Metzger et al. 1997 Wavelength Optical Emission Absorption Mg II Mg II I Fe II flux Fe II Wavelength GRB970508 – Absorption Lines: z=0.835
Host Galaxy Detected for GRB970508 Z=0.835 flux Wavelength
Radio Twinkling can also be used to estimate the GRB distance: consistent with z=0.835 Just as the Earth’s Atmosphere Causes light To scatter Causing point Sources to “twinkle”, the Interstellar Medium causes Radio emission To twinkle. When The burst gets Large enough, Like planets, the Twinkling stops.
Waxman, Kulkarni, & Frail 1997 T=t, r=c t Where c is speed of light T=0, point Source ISM Scattering Twinkle, Twinkle Observer Always Sees Part of Burst
A crash Course in Scintillations Scintillations determine the size of the source in a model independent way. The size (~1017cm) is in a perfect agreement with the prediction of the Fireball model.
HETE2 Fregate: 6-400 keV GRB triggers and low res. Spectra WXM 2-25 keV, medium energy resolution and 10arcmin localization SXC 0.5-10 keV, good energy resolution and 1arcmin localization
Burst Alert Telescope (BAT) - 32,000 CdZnTe detectors - 2 sr field of view X-Ray Telescope (XRT) - CCD spectroscopy - Arcsec GRB positions UV-Optical Telescope (UVOT) - Sub-arcsec position - 22 mag sensitivity Spacecraft slews XRT & UVOT to GRB in <100 s Swift: a new era for GRB studied
XRF Short GRB XRF XRF XRF XRF Short GRB XRF XRF Short GRB Short GRB Short GRB XRF Short GRB XRF XRF XRF Short GRB Short GRB Short GRB Swift GRBs
• elliptical hosts • low SF rates • offset positions • redshifts z ~ 0.2 >> inconsistent with collapsar model >> supportive of NS-NS model XRT XRT BAT Chandra Swift localizes short GRBs
Il GRB piu’ lontano, quello piu’ brillante e quello piu’ energetico GRB080913 GRB080916C Fermi -rays GRB080319B
Subaru Spectroscopy 3 GRB @ z>6 GRB050904 Ly break in the IR J=17.6 at 3.5 hours
Observational Constraints on the Central Engine • Host Galaxies • GRB Environments • Prompt Emission • Bumps in the Afterglow (SN?) • Energetics and Beaming • Using GRBs as Cosmological Probes
I: Host Galaxies Accurate positions Allowed Astronomers To watch the bursts Fade, and then Study their Host Galaxy! Host Galaxy The fading optical afterglow of GRB 990123 as seen by HST on Days 16, 59 and 380 after the burst. Optical Afterglow
Properties Of Host Galaxies I) Like Many Star-forming Galaxies At that Observed redshift Holland 2001 II) Star-formation rates high, but consistent With star forming galaxies.
Location, Location, Location(In addition to detecting hosts, we can determine where a burst occurs with respect to the host.
GRB hosts • GRBs trace brightest regions in hosts • Hosts are sub-luminous irregular galaxies • Concentrated in regions of most massive stars • Restricted to low metallicity galaxies
If we take These Positions At face Value, We can Determine The Distribution Of bursts With respect To the half- Light radius Of host Galaxies! This Will Constrain The models! Distribution Follows Stellar Distribution
GRB Hosts Exhibit Larger Mg line Equivalent Widths Than QSO absorbers: Higher Density? Fiore 2000 Salamanca et al. 2002 Savaglio, Fall & Fiore 2003