1. The Transient Universe: AY 250 Spring 2007 Existing Transient Surveys: High Energy I: Gamma-Ray Bursts Geoff Bower

2. The Transient Universe: AY 250 Spring 2007 Klebesadel etal 1973

3. The Transient Universe: AY 250 Spring 2007 Vela Satellites Orbiting Earth at 10^5 km –Equally spaced 0.2 – 1.5 MeV sensitivity Isotropic sensitivity Part of military program to detect space- and atmospheric-nuclear explosions

4. The Transient Universe: AY 250 Spring 2007 GRBs and Evidence for Cosmic Origin 16 bursts over 3 years 0.1 – 30 s duration No evidence for cosmic rays in other detectors Time of arrival delay between satellites < 0.8 s ~ –Accuracy of 0.05 s Intersection of great circles indicates non- solar, non-terrestrial origin –Mirror image degeneracy –Except one No connection with solar activity Equal flux in all detectors –No inverse square loss

5. The Transient Universe: AY 250 Spring 2007 Two Incredible Things Search motivated by theory: –GRBs predicted from supernovae (Colgate 1968) The right answer to GRB puzzle 25 years before evidence Postulate incredible distance of 1 Mpc –10^46 ergs s^-1 The lack of information in the paper –Dates –Coordinates –Fluxes

6. The Transient Universe: AY 250 Spring 2007 X-ray through Gamma-ray Detection Multi-satellite detection UCSD satellites directional Unambiguous direction determination –Error of 5 deg Wheaton et al 1973

7. The Transient Universe: AY 250 Spring 2007 More Early Observations

8. The Transient Universe: AY 250 Spring 2007 Some Early Conclusions Emission peaks around 100 kev 0.1 sec variability time scale  size < 3 x 10^9 cm No optical counterparts Integrated emission from GRBs < G-ray background Gamma-ray stars? –10^36 ergs s^-1

9. The Transient Universe: AY 250 Spring 2007 An Explosion of Observation & Theory 1973-1995: 2000 papers 1973-1991: Total number of bursts ~ few hundred –From wide range of instruments Galactic NS-NS merger is leading hypothesis for 15 years

10. The Transient Universe: AY 250 Spring 2007 Interplanetary Network Small detectors on multiple space craft 2 deg accuracy 0.1 sec timing accuracy

11. The Transient Universe: AY 250 Spring 2007 BATSE 8 detectors on CGRO Launched in 1991 De-orbited in 2000 Fishman & Meegan 1995

12. The Transient Universe: AY 250 Spring 2007 A Wide Variety of Light Curves

13. The Transient Universe: AY 250 Spring 2007 Bimodal Burst Distribution

14. The Transient Universe: AY 250 Spring 2007 Short-Hard Bursts vs. Long-Soft Bursts

15. The Transient Universe: AY 250 Spring 2007 Flux Distribution  Inhomogeneity N ~ S^-3/2

16. The Transient Universe: AY 250 Spring 2007 Test Classic test of spatial inhomogeneity –Schmidt 1968 Vmax = maximum volume in which signal can be detected = ½ for homogeneous distribution _BATSE = 0.32 +/- 0.01 –Do not detect the most distant bursts _Bright burst = 0.46 +/- 0.02

17. The Transient Universe: AY 250 Spring 2007 Angular Distribution  Isotropy

18. The Transient Universe: AY 250 Spring 2007 Anisotropic Distributions

19. The Transient Universe: AY 250 Spring 2007 No Repetition of Bursts Angular Correlation Function Meegan et al 1995

20. The Transient Universe: AY 250 Spring 2007 Time Dilation of Bursts Norris et al 1994

21. The Transient Universe: AY 250 Spring 2007 Galactic vs. Extragalactic No bias towards galactic disk Isotropy of the weakest bursts  Galactic halo –R > 100 kpc –Ejected neutron stars? –Absence of M31 GRBs is constraint Isotropic Spatial inhomogeneity due to evolution Weakest sources at z~1

22. The Transient Universe: AY 250 Spring 2007 Afterglows Discovered Van Paradijs et al 1997 970228 Galaxy host

23. The Transient Universe: AY 250 Spring 2007 Afterglows Discovered GRB 970508 Radio afterglow seen Interstellar scintillation –Size < 3 microarcsec ~ 10^17 cm –V ~ R/2 weeks ~ 4c Frail et al 1997

24. The Transient Universe: AY 250 Spring 2007 Afterglow Redshift 970508 Z=0.835 Metzger 1997

25. The Transient Universe: AY 250 Spring 2007 Beppo Sax BATSE: 3 deg error Beppo Sax: 3 arcmin

26. The Transient Universe: AY 250 Spring 2007 The Achromatic Jet Break Panaitescu 2005

27. The Transient Universe: AY 250 Spring 2007 Jet Beaming & Standard Energy Frail et al 2001

28. The Transient Universe: AY 250 Spring 2007 Swift Complicates the Picture