Short Gamma Ray Bursts Curtis DeWitt

BATSE catalog 30 % shorter than 2s Histogram

Isotropic Distribution on sky Cosmological Origin Bright --- like supernovae, but much faster

Candidate Systems Core collapse SN Magnetars Coalescing Binary bare degenerate star? Pop III hypernovae? Magnetars Coalescing Binary NS-NS NS-BH

What is the burst itself? Ultra Relativistic (>1000) fireball made of positron/electron plasma, neutrinos, photons collides with itself (reverse shock) and with the ISM (forward shock) creating a burst of gamma rays  is Lorentz factor t=t' p= m v L=L0 E=  m c2

What can you tell from the burst lightcurve and afterglows? L ~ t^-n n, or change in n tells you stuff like jet opening angles hardness ratio duration

Long Bursts are the Core Collapse SN BeppoSAX finds x-ray afterglows around 97, a few dozen are known Localized long GRBs are found centered in star forming galaxies (50 M/yr) (H-alpha emission, UV continuum) They should last for ~10s if they are Supernovae

Short Bursts Predictions: associated with early type galaxies (old stars) scatter in offset from galaxy-- combination of kicks and coalescence timescales dimmer /quickly fading afterglows due to low density ISM around NS-NS binary must happen after most star forming activity, z<1

Short Bursts

Localizing Short Bursts

Localizing Short Bursts The Results GRB 050509B May 9, 2005 z~0.225, elliptical host GRB 050709 July 9, 2005 z~0.16, star forming irregular host GRB 050724 July 24, 2005 z~0.257, elliptical host

GRB 050509B

GRB 050509B SWIFT detection BAT finds it to within 2.3' XRT 9.3”, 62 s later (11photons withing 1600 s) UVOT-- nothing (also 62 s later) Chandra- nothing short/hard- 50-100keV/25keV~1.4

GRB 050509B: the Host 9.8” from Giant Elliptical (4E11L) Probability(<10”) ~ 10^-3 No other GRB (of ~80) were this close to a elliptical UVOT images galaxy, 200nm flux limit says < 0.2 M/yr star formation--- not a lot Lots of GC in ellipticals Coalescence takes 2x10^8 yrs, SN Ia kick velocities are 100-1000km/s-- could take the system out to 100kpc--- this ones at 35kpc, projected

GRB050709

GRB050709 HETE short/hard z=0.160 Chandra detection, good localization an irregular star forming galaxy, but SN not visible (must have been dimmer than -12 in R absolute) Probably another coalescing binary

GRB050709

GRB050724

GRB050724 Swift- 74 seconds 4kpc in projection from elliptical galaxy 0.4 scale lengths (interior to distribution of long bursts) no emission lines in galaxy spectra z=0.258 no Hbeta-- stars older than 1 Gyr, less than 0.02M/yr formation