1. Short Gamma Ray Bursts
Curtis DeWitt

2. BATSE catalog
30 % shorter than 2s
Histogram

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

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

5. 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

7. 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

8. 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

9. 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

10. Short Bursts

11. Localizing Short Bursts

12. Localizing Short Bursts
The Results
GRB B May 9, z~0.225, elliptical host
GRB July 9, z~0.16, star forming irregular host
GRB July 24, z~0.257, elliptical host

13. GRB B

14. 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 keV/25keV~1.4

15. 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 km/s-- could take the system out to 100kpc--- this ones at 35kpc, projected

16. GRB050709

17. 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

18. GRB050709

19. GRB050724

20. 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