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GRB Theory and observations 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) 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 GRB light curves GRBs: flashes of 0.1 MeV gamma rays that last 1-100 s -ray observations summary • Isotropy in the sky • Duration: T90 • Variability: 0.2 s short 20 s long Most show t ~ 64 ms Some t ~ 1 ms • 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. First Detected Gamma-Ray Burst 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 X-ray Novae II) Comets • Neutron Star Quakes • Magnetic Reconnection Galactic Gamma-Ray Bursts: Soft Gamma-Ray Repeaters One Class of GRBs Is definitely Galactic: Soft gamma-ray Repeaters (SGRs) Characteristics: 1) Repeat Flashes 2) 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 (106-10-5 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 Collapsar Model – Collapse of a Rotating Massive Star into a Black Hole Main Predictions: Beamed Explosion, Accompanying supernova-like explosion Stan Woosley BATSE - Burst And Transient Spectrometer Experiment BATSE Module 8 Detectors Almost Full Sky Coverage Few Degree Resolution 20-600keV BATSE Consists of two NaI(TI) Scintillation Detectors: Large Area Detector (LAD) For sensitivity and the Spectroscopy Detector (SD) for energy coverage Galactic Models BATSE Results – Isotropy Cosmological Models Favored! 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 Gamma-Ray Burst Duration vs. Energy Spectrum 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 BeppoSAX Instruments LECS/MECS • Xenon Gas Scintillator • Energy Range: .11keV (1-10keV) • ~1 arc minute resolution • Goal – Localize Object HPGSPC PDS • 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: 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! Metzger et al. 1997 flux GRB970508 – Absorption Lines: z=0.835 Wavelength Optical Emission Absorption Fe II Fe II Mg II I flux Mg II Wavelength Host Galaxy Detected for GRB970508 flux Z=0.835 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=0, point Source T=t, r=c t Where c is speed of light 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. GRB971214 @z=3.42 GRB NH and AV 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 Swift: a new era for GRB studied 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 GRBs XRF Short GRB XRF XRF XRF XRF Short GRB XRF Short GRB Short GRB Short GRB XRF XRF Short GRB XRF Short GRB XRF XRF Short GRB Short GRB Swift localizes short GRBs XRT BAT • elliptical hosts • low SF rates • offset positions • redshifts z ~ 0.2 >> inconsistent with collapsar model >> supportive of NS-NS model XRT Chandra Il GRB piu’ lontano, quello piu’ brillante e quello piu’ energetico GRB080913 GRB080916C Fermi -rays QuickTime™ e un decompressore Animation sono necessari per visualizzare quest'immagine. GRB080319B 3 GRB @ z>6 GRB050904 Ly break in the IR J=17.6 at 3.5 hours Subaru Spectroscopy 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! The fading optical afterglow of GRB 990123 as seen by HST on Days 16, 59 and 380 after the burst. Host Galaxy 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 Distribution Follows Stellar Distribution If we take These Positions At face Value, We can Determine The Distribution Of bursts With respect To the halfLight radius Of host Galaxies! This Will Constrain The models! GRB Hosts Exhibit Larger Mg line Equivalent Widths Than QSO absorbers: Higher Density? Fiore 2000 Salamanca et al. 2002 Savaglio, Fall & Fiore 2003 Results from low resolution spectroscopy High dust depletion High dust content Denser clouds Savaglio, Fall & Fiore 2003 2) Metallicity depends on galaxy mass Savaglio et al. 2008 Berger et al. 2006 Star-formation rate in GRB hosts Savaglio+ 2008 What we’ve learned from GRB Hosts! • Hosts of long GRBs are star-forming galaxies • GRBs trace the stellar distribution (in distance from galaxy center) • GRBs occur in dense environments (star forming regions?) Using GRBs as Cosmological Probes Gamma-Ray Bursts are observed at extremely high redshifts and can be used to study the early universe. • Star Formation History • Beacons to direct large telescopes to study nascent galaxies • Studies of intervening material between us and GRB – akin to quasar absorption studies METAL ABUNDANCES IN HIGH z GALAXIES GRB explosion site Circumburst environment Host gas far away To Earth Redshift Distribution Of GRBs With known Redshifts (2002) Redshifts As high as 5 observed! Lloyd-Ronning et al. 2002 Lloyd-Ronning, Fryer, & Ramirez-Ruiz 2002 Solid squares Denote bursts With observed Redshifts. Open squares Denote Positions using A LuminosityVariability Relation. (Fenimore & Ramirez-Ruiz 2000). Dashed line Artifact of Luminosity Cut-off in FR-R Sample. Redshift distributions Pre-Swift Swift 0 1 2 4 Redshift (z) 13 Galaxies Quasars GRBs 10 12 10 8 High resolution spectroscopy: GRB021004 FORS1 R~1000 CIV CIV z=2.296 z=2.328 UVES R=40000 z=2.296 z=2.328 GRB050730 UVES spectrum GRB locations within galaxies GRBs show higher gas densities and metallicities, And have significantly lower [(Si,Fe,Cr)/Zn] ratios, Implying a higher dust content: Star Formation Region History of metal enrichment 000926 050820 050401 060206 030323 050904 050730 Savaglio+2003 Prochaska+ 2003 GRB host galaxy metallicities However… metallicity depends on: 1)Impact factor 2)Galaxy mass 3)Star-formation rate 4)Etc…. 1) Metallicity depend on impact factor GRB021004 Variability GRB060418 z=1.49 VLT/UVES Vreeswijk et al. 2007 Intervening absorbers Ly forest: deviation from what is already known from quasar forests. ``Proximity effect'' should be much reduced for GRBs. An accurate determination of dn/dz at high z has strong implications for investigations of the re-ionization epoch, since the optical depth due to Ly line blanketing is evaluated by extrapolating the Ly dn/dz measured at lower-z. MgII and CIV absorbers: Incidence of MgII absorbers ~4 times higher than along QSO sight-lines. Incidence of CIV absorbers similar… WHY??? Dust composition/evolution the case of GRB 050904 @z=6.3 Large X-ray absorption and UV dust extinction Haislip WFCAMUKIRT ~0.5 days, Ly corr. = 3.02 Tagliaferri FORSVLT ~1 day, Ly corr. = 1.27 Haislip GMOSGemini ~3 days, Ly corr. = 2.38 GRB 050904 z=6.3 Stratta et al 2007 [email protected] extinction curve 0.5 day A3000=0.89+\-0.16 1 day A3000=1.33+\-0.29 3 days A3000=0.46+\-0.28 NH~1023 cm-2 AV/NH~50 times lower than Galactic!! @z~6 no dust from AGB stars. Only sources are CCSNe (and AGNs) Much less dust and much smaller AV/NH GRB Environments II: Studying the environment using radio and optical observation of GRBs • Density profiles are different for different environments: massive stars will be enveloped by a wind profile. • These different density profiles produce different radio, optical emission. The Density Profile from Winds ISM density is constant The Shock Radius Depends On the Density Profile! Radio And Optical Light Curves Are a Function Of this Radius! GRB021004 For Many Gamma-Ray Bursts, Wind-swept Environments Best fit the Data (radio And R-band Data best Diagnostics! Roger Chevalier Li & Chevalier 2003 On the Surface, It appears we Can constrain The environments, But, beware, There still remain Many free Parameters in These calculations! The connection between SNe and GRBs Afterglow and GRB Energetics IV: • As we learned yesterday, afterglows allowed us to calculate redshifts. • Assuming a cosmology, we can then get distances. • Assuming isotropic explosions, we can estimate the GRB energies! These energies range over many orders of magnitude. GRB Redshifts (2000) GRB Redshift Isotropic Energy GRB Redshift Isotropic Energy GRB970228 0.695 5x1051 GRB990308 >1.2? NA GRB970508 0.835 8x1051 GRB990506 1.3 NA GRB970828 0.958 NA GRB990510 1.619 3x1053 GRB971214 3.418 3x1053 GRB990705 0.86 NA GRB980326 1? 3x1051 GRB990712 0.430 NA GRB980329 2 or 3-5 NA GRB991208 0.706 1.3x1053 GRB980425 0.0085 1048 GRB991216 1.02 6.7x1053 GRB980613 1.096 NA GRB000131 4.5 1054 GRB980703 0.966 1x1053 GRB000418 1.118 5x1052 GRB990123 1.600 3x1054 GRB000926 2.066 2.6x1053 Afterglow and GRB Energetics • As we learned yesterday, afterglows allowed us to calculate redshifts. • Assuming a cosmology, we can then get distances. • Assuming isotropic explosions, we can estimate the GRB energies! These energies range over many orders of magnitude. • But are GRBs isotropic? Jet Signatures E (1 cos b )E ,iso f b (1 cos b ) b /2 2 n o b E ,iso 1/ 8 t break 1 z 3/8 Stanek et al. (2001) GRB 010222 Energy and Beaming Corrections • 15 events with z and t_jet • • The dispersion in isotropic GRG energies results from a variation in the opening (or viewing) angle The mean opening angle is about 4 degrees (i.e. fb-1 ~ 500 ) Geometry-corrected energies are narrowly clustered (1=2x) E 5 1050 erg (for n o 0.1 cm -3 assumed) Frail et al. (2001) Energy and Beaming (Continued) 24 events with z and t_jet • • Outliers Improved analysis • Larger sample • Used measured densities • Error propagation Geometrically corrected gamma-ray energy … E 1.3 1051 erg • • Bloom, Frail & Kulkarni (2003) Increase is due to using real density values 1 of 0.35 dex (2.2x) Summary of GRB Energetics • Gamma-ray bursts and their afterglows have (roughly) standard energies E 10 51 erg E k 10 51 erg • Robust result using several complementary methods E gamma-rays Ek X-rays Ek BB modeling Ek Calorimetry E shock E E k few 1051 erg E / E shock 0.5 SN/GRB connection! GRBs have SN-like outbursts. But these bursts are beamed, and we won’t see all explosions as a GRB. What do we make of the SN/GRB connection: I) All GRBs produce SNe? II) All SNe are GRBs (only those observed along the jet axis are GRBs)? Are either of these true? Ambitious Theorists – New SN Mechanism • Collapsar Theorists argue I) is true, but not II) • Others argue that all supernovae have jets (e.g. asymmetries in SN1987A) and the standard SN engine is wrong! • SN-like is NOT SN What fraction of SNe are GRBs? The GRB community tends to not talk to the SN community. Hence this problem has lingered for a long time. The simple fact is that the SN-like spectra and lightcurves are quite different than true SNe. But let’s assume we don’t know this, how else can we tell? - Radio! A Complete Radio Catalog • 5 yr period (1997-2001) • BeppoSAX, IPN, RXTE and HETE satellites • 75 GRBs searched for radio AGs • searches at 5 and 8.5 GHz • frequencies 0.8-650 GHz • 1521 flux density measurements (or limits) • 2002-2003 data on Web Frail, Kulkarni, Berger and Wieringa AJ May 2003 http://www.aoc.nrao.edu/~dfrail/grb_public.shtml Cumulative Flux Density Distribution 50 % • Max radio flux 2 mJy • 19 detections – mean=315+/-82 uJy • 44 GRB in total – mean = 186+/-40 uJy • 50% of all bursts are brighter than 110 uJy • Radio afterglow observations are severely sensitivity limited! Complete sample of 44 GRBs with 8.5 GHz measurements made between 5 and 10 days post-burst Spectral Radio Luminosity L 4d 2L F (1 z ) 1 where F t mean 1031 erg s -1 Hz -1 SN1993J 2 10 27 erg s -1 Hz -1 F 2 108 ! R FR Complete sample of 18 GRBs with redshifts and 8.5 GHz measurements made between 5 and 10 days post-burst Fireball Calorimetry Frail, Waxman & Kulkarni (2000) E o 5 1050 erg n o 1 cm -3 • Long-lived radio afterglow makes a transition to NR expansion – no geometric uncertainties – can employ robust Sedov formulation for dynamics – compare with equipartition Most energy estimates require knowledge of the geometry of the outflow – radius and cross check with ISS-derived radius • Limited by small numbers How Common are EnginePowered SNe? VLA/ATCA survey of 34 Type Ib/c SNe to detect off-axis GRBs via radio emission Berger PhD • Most nearby SNe Ib/c do not have relativistic ejecta • Two distinct populations • Ek(GRB)<<1 foe (hydo collapse) • <10% are 1998bw-like