1. Neutron Stars and Black Holes
Remnant cores of massive stars: produce pulsars, jets and gamma-ray bursts
Relativity theory is needed!

2. Results of 2nd Exam Raw mean: 54.92; so curve of 20 pts
Curved mean: 74.92;  = 9.80
Distribution: High, 100; Low, ≥ 90: ≥ 80: 15
≥ 70: 16
≥ 60: 13
< 60: 3
Random guessing: 52 (after curve) -- no one did that badly

3. It’s Hard to Find Black Holes
They don’t emit (significant) radiation
Light bending means they don’t even show up as dark spots: 
Unless distance is close to RS, gravity is close to that of a regular star of the same mass

4. Origin of Black Holes
Collapse of very massive stars (>30 M) can lead to BHs of ~3-25 M (neutron stars must have masses below about 2 M ).
A NS could accrete more gas from a binary companion, kicking it over the upper mass limit
Collapse of densest regions of forming galaxies, either directly or through merger of stars in dense clusters can yield BHs with M > 1000 M .
Quantum fluctuations in the early universe could give primordial BHs of a wide range of masses.

5. Accretion Disks
Form when gas spirals down into a massive object. Seen in:
Stars (and planetary systems) being born (earlier)
Binary stellar systems with compact component: white dwarf neutron star black hole
Active Galactic Nuclei (later)

6. In an Accretion Disk Mass moves inward
Angular momentum is carried outward
Friction (viscosity) in the gas heats it up
Usually most of this heat is radiated from the disk surface giving:
Ultraviolet radiation from white dwarfs
X-rays from neutron stars and stellar mass BHs
Mostly visible and UV from AGN BHs
Most logical way to launch jets

7. One famous X-ray binary with a very likely black hole is in the constellation Cygnus

8. Cyg X-1: Radio Image & X-ray light curve
Combining observations: optical of blue giant; Doppler shifted lines of star and gas stream we conclude star has M>15 M and X-ray emitting companion has M>10 M, so

9. Cygnus X-1 is a Black Hole Binary

10. Accretion Disks are Efficient
E = mc2
Complete conversion of mass to energy is only possible in matter-antimatter annihilation
But normal accretion disks can convert > 5.7% but probably < 32% of mass to energy
This is far better than chemical reactions (~ %) or even nuclear fusion (~0.7 %)
Full conversion of 1 M /year = 5.7  1039W

11. Jets Launched From Disks
Artist’s rendition of jets launched from vicinity of BH in the center of an AD.

12. Gamma-Ray Bursts
Tremendous powers in high energy photons emitted in just a few seconds
First discovered by spy satellites in 1960s looking for atomic bomb tests: isotropic in the sky
Usually have “afterglows”: emission in X-rays, optical and radio bands that decay more slowly
Generic model: a “fireball” of very hot plasma, bursting out as a very relativistic jet (~100)
This makes it look even brighter if jet points at us, but still involves great powers, since many are very distant

13. Where do gamma-ray bursts come from?

14. GRB Light Curves and Locations

15. GRBs are Far Away
Since 1997 many have had galaxies identified as their hosts; at large cosmological redshifts, therefore billions of parsecs away

16. Competing Models: NS-NS Mergers or Hypernovae (or both)?

17. Some GRBs are Hypernovae
Light curves brightening and looking like SN have been seen in a few cases, making it likely that some (many?, all?) GRBs are exceptionally powerful SN
But could just be long GRBs, w/ short ones NS-NS mergers.

18. End of Stars We now turn to collections of stars
Galaxies, starting with our Home Galaxy
Clusters and superclusters of galaxies
Then the whole Universe:
Cosmology and the
Big Bang