GRB Theory and observations Useful reviews: Waxman astro-ph/ Ghisellini astro-ph/ Piran astro-ph/ Meszaros astro-ph/ Gehrels 2009 ariv: Useful links:(Chris Fryer lectures) GRBs most luminous objects in the Universe!! Sun Luminosity L ~4 erg/s Supernova L~10 51 erg/s Galaxies with nuclei L~10 48 erg/s GRB luminosity L~10 52 erg/s GRB light curves GRBs: flashes of 0.1 MeV gamma rays that last s Isotropy in the sky Duration: Duration: T 90 0.2 s short 20 s long Flux: f = erg/cm 2 s Flux: f = erg/cm 2 s Rate R 300/yr BATSE and 100/yr Swift Rate R 300/yr BATSE and 100/yr Swift -ray observations summary Variability: Variability: Most show t ~ 64 ms Some t ~ 1 ms GRB 3 July 1969: first detection of a GRB by Vela 5A Vela Satellites 10 5 km Orbits Launched in pairs launched 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 Earths 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: 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 5 th event Models for SGRs Accretion I) Binary Companion - no companion seen II) SN Fallback Too long after explosion Magnetic Fields ~10 15 G Fields - Magnetars Extragalactic Models Large distances means large energy requirement (10 51 erg) Event rate rare ( 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 Stan Woosley 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 keV Galactic Models BATSE Results Isotropy Cosmological Models Favored! Gamma-Ray Burst Lightcurves GRB Lightcurves have A broad range of Characteristics Fast Rise Exponential Decay FREDs GRB GRB990316 Gamma-Ray Burst Durations Two Populations: Short s Long s 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 inconsistent with collapsar model >> supportive of NS-NS model BAT XRT Chandra Il GRB piu lontano, quello piu brillante e quello piu energetico GRB080319B GRB GRB080916C Fermi -rays 3 z>6 Subaru Spectroscopy GRB 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 The fading optical afterglow of GRB as seen by HST on Days 16, 59 and 380 after the burst. Accurate positions Allowed Astronomers To watch the bursts Fade, and then Study their Host Galaxy ! 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 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 Savaglio, Fall & Fiore 2003 Results from low resolution spectroscopy Savaglio, Fall & Fiore 2003 High dust depletion High dust content Denser clouds 2) Metallicity depends on galaxy mass Savaglio et al Berger et al. 2006 Star-formation rate in GRB hosts Savaglio+ 2008 What weve 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 To Earth Host gas far away Redshift Distribution Of GRBs With known Redshifts (2002) Redshifts As high as 5 observed! Lloyd-Ronning et al. 2002 Solid squares Denote bursts With observed Redshifts. Open squares Denote Positions using A Luminosity- Variability Relation. (Fenimore & Ramirez-Ruiz 2000). Dashed line Artifact of Luminosity Cut-off in FR-R Sample. Lloyd-Ronning, Fryer, & Ramirez-Ruiz 2002 Redshift distributions Redshift (z) Pre-Swift Swift Galaxies Quasars GRBs Distance (Billion Light Years) High resolution spectroscopy: GRB FORS1 R~1000 CIV CIV z=2.296 z=2.328 UVES R=40000 z=2.296 z=2.328 GRB UVES spectrum GRBs show higher gas densities and metallicities, And have significantly lower [(Si,Fe,Cr)/Zn] ratios, Implying a higher dust content: Star Formation Region GRB locations within galaxies History of metal enrichment Savaglio+2003 Prochaska 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 GRB 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 Large X-ray absorption and UV dust extinction Haislip WFCAM- UKIRT ~0.5 days, Ly corr. = 3.02 Tagliaferri FORS- VLT ~1 day, Ly corr. = 1.27 Haislip GMOS- Gemini ~3 days, Ly corr. = 2.38 GRB z=6.3 Stratta et al 2007 extinction curve 0.5 day A 3000 =0.89+\ day A 3000 =1.33+\ days A 3000 =0.46+\-0.28 N H ~10 23 cm -2 A V /N H ~50 times lower than no dust from AGB stars. Only sources are CCSNe (and AGNs) Much less dust and much smaller A V /N H 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! For Many Gamma-Ray Bursts, Wind-swept Environments Best fit the Data (radio And R-band Data best Diagnostics! Li & Chevalier 2003 Roger Chevalier GRB021004 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. GRBRedshiftIsotropic Energy GRB x GRB x GRB NA GRB x GRB ?3 x GRB or 3-5NA GRB GRB NA GRB x GRB x GRB Redshifts (2000) GRBRedshiftIsotropic Energy GRB990308>1.2?NA GRB NA GRB x GRB NA GRB NA GRB x GRB x GRB GRB x GRB x 10 53 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 GRB Stanek et al. (2001) Piran, Science, 08 Feb 2002 Energy and Beaming Corrections 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. f b -1 ~ 500 ) Geometry-corrected energies are narrowly clustered (1 =2x) Frail et al. (2001) 15 events with z and t_jet Energy and Beaming (Continued) Improved analysis Larger sample Used measured densities Error propagation Geometrically corrected gamma-ray energy Increase is due to using real density values 1 of 0.35 dex (2.2x) Bloom, Frail & Kulkarni (2003) 24 events with z and t_jet Outliers Summary of GRB Energetics Gamma-ray bursts and their afterglows have (roughly) standard energies Robust result using several complementary methods E gamma-rays E k X-rays E k BB modeling E k Calorimetry SN/GRB connection! GRBs have SN-like outbursts. But these bursts are beamed, and we wont 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 lets assume we dont know this, how else can we tell? - Radio! A Complete Radio Catalog 5 yr period ( ) BeppoSAX, IPN, RXTE and HETE satellites 75 GRBs searched for radio AGs searches at 5 and 8.5 GHz frequencies GHz 1521 flux density measurements (or limits) data on Web Frail, Kulkarni, Berger and Wieringa AJ May 2003 Cumulative Flux Density Distribution 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 50 % Spectral Radio Luminosity Complete sample of 18 GRBs with redshifts and 8.5 GHz measurements made between 5 and 10 days post-burst Fireball Calorimetry 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 Frail, Waxman & Kulkarni (2000) How Common are Engine- Powered 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 E k (GRB)