1. The general theory of relativity is our most accurate description of gravitation Published by Einstein in 1915, this is a theory of gravity A massive object causes space to curve and time to slow down These effects manifest themselves as a gravitational force These distortions of space and time are most noticeable in the vicinity of large masses or compact objects

2. The general theory of relativity also predicts the existence of gravitational waves, which are ripples in the overall geometry of space and time produced by moving masses Gravitational waves have been detected indirectly, and specialized antennas are under construction to make direct measurement of the gravitational waves from cosmic cataclysms

7. If a stellar corpse has a mass greater than about 2 to 3 M , gravitational compression will overwhelm any and all forms of internal pressure The stellar corpse will collapse to such a high density that its escape speed exceeds the speed of light

8. Supermassive black holes exist at the centers of most galaxies These are detected by observing the motions of material around the black hole

9. Falling into a black hole is an infinite voyage

10. ●Could a black hole somehow be connected to another part of spacetime, or even some other universe? ●General relativity predicts that such connections, called wormholes, can exist for rotating black holes

11. Black holes evaporate

12. Black Holes have no Hair Properties of a black hole: - Mass - Spin (angular momentum) - Charge (tends to be zero)

13. Black Holes can have impact on their environments

14. Do Black Holes Really Exist? Good Candidate: Cygnus X-1 - Binary system: 30 M Sun star with unseen companion. - Binary orbit => companion > 7 M Sun. - X-rays => million degree gas falling into black hole.

15. Vela satellite An early gamma ray-burst

16. A Gamma Ray Burst Sampler

17. Great debate: 1967-1997

18. GRBM: 40-600 keV WFC: 2-30 keV NFI: 2-10 keV Bepposax Satellite

19. X-Ray Afterglow from GRB 971214 t=6.5 hrst=12.5 hrst=54 hrs

20. Optical Afterglow from GRB 971214 Host HST Image Keck Images 2 days2 months

21. Optical Afterglow from GRB 080319b Swift Image Light Curve Naked-eye visible for ~30 sec. Distance = 7.5 billion ly

22. Uh-oh

23. GRB Host Galaxies Bloom et al. 2002

24. Radio Light Curves from long GRBs

25. GRB 970508 First VLBI detection of a GRB Afterglow absolute position to < 1 mas Size < 10^19 cm (3 lt years) Distance > 10000 lt years Taylor et al 1997

26. R ~ (E/n)^1/8 Relativistic Expansion v ~ 0.96c E ~ 10^53 ergs (isotropic equivalent) Taylor et al 2004 Pihlstrom et al 2007 GRB Expansion

27. The Evidence (long GRBs) ● Peak toward low end of gamma-ray, complex gamma-ray light curves ● Often have bright afterglows ● Evidence for a relativistic explosion ● Energy required of ~ 10 53 ergs (isotropic) ● Associated with regions of star formation in distant galaxies (out to edge of observable universe) ● Sometimes obscured by dust ● Plus …

28. Example Supernova: 1998bw

29. Long GRBs clearly connected to Supernovae Hjorth et al 2003

30. 1. White Dwarf If initial star mass < 8 M Sun or so 2. Neutron Star If initial mass > 8 M Sun and < 25 M Sun 3. Black Hole If initial mass > 25 M Sun Final States of a Star No Event + PN Supernova + ejecta GRB + Supernova + ejecta

31. Clicker Question: What is the remnant left over from a GRB? A: a white dwarf + expanding shell B: a neutron star + expanding shell C: a black hole + expanding shell D: no remnant, just the expanding shell

32. Clicker Question: Where do most GRBs occur: A: in globular clusters B: in star forming regions C: in old open clusters D: in the Oort cloud

33. Clicker Question: What was the subject of the great debate about GRBs that went on for ~30 years? A: If they were produced by Supernovae or colliding stars. B: If they were galactic or extragalactic in origin. C: If they were of terrestrial or extraterrestrial in origin? D: If a nearby GRB killed off the dinosaurs.

34. Coalescence versus Collapse NS-NS binaryMassive star