1. YSS - Intro. to Observational Astrophysics (ASTR 205). Class #10 The Bizarre Stellar Graveyard (Chapter 13) Professor: José Maza July 3, 2012 Professor: José Maza July 3, 2012

2. White Dwarfs Degeneracy pressure The star is supported by electron degeneracy pressure A teaspoon of white dwarf matter would weigh several tons. Degeneracy pressure The star is supported by electron degeneracy pressure A teaspoon of white dwarf matter would weigh several tons.

3. Sirius B was the first white dwarf to be discovered

5. What can happen to a white dwarf in a close binary system? The white dwarf would generate an accretion disk. What can happen to a white dwarf in a close binary system? The white dwarf would generate an accretion disk.

7. Novae Binaries with a white dwarf accreting material from a red giant. The material forms an accretion disc around the white dwarf. A layer of Hydrogen rich material covers the white dwarf surface. When density and temperature of the layer are high enough the Hydrogen is fussed into Helium Binaries with a white dwarf accreting material from a red giant. The material forms an accretion disc around the white dwarf. A layer of Hydrogen rich material covers the white dwarf surface. When density and temperature of the layer are high enough the Hydrogen is fussed into Helium

10. White dwarf supernovae Chandrasekhar´s limit 1.4 M  When a carbon WD reaches a mass near 1.4 M   its temperature rises high enough for carbon fusion to ignite. White Dwarf Supernova Chandrasekhar´s limit 1.4 M  When a carbon WD reaches a mass near 1.4 M   its temperature rises high enough for carbon fusion to ignite. White Dwarf Supernova

12. Neutron Stars Radius 10 km Neutron degeneracy pressure supports neutron stars. Density ≈ 10 15 g/cm 3 Radius 10 km Neutron degeneracy pressure supports neutron stars. Density ≈ 10 15 g/cm 3

14. In 1967 graduate student Jocelyn Bell working at Cambridge discovered a new type of radio source. These sources emitted a periodic pulse with a very short period 1.337 seconds. These sources were named PULSARS. In 1967 graduate student Jocelyn Bell working at Cambridge discovered a new type of radio source. These sources emitted a periodic pulse with a very short period 1.337 seconds. These sources were named PULSARS.

16. Crab Pulsar

17. Crab Nebula

21. Black Holes Escape velocity grows if the radius decreases. There is a radius at which the escape velocity approaches the speed of light. Schwarzschild radius. Escape velocity grows if the radius decreases. There is a radius at which the escape velocity approaches the speed of light. Schwarzschild radius.

24. Black holes Event horizon Schwarzschild radius Event horizon Schwarzschild radius

28. Gamma-Ray Bursts In 1973 the first Gamma Ray Burst was announced. At first it was thought these were just a variation of the X-Ray burst that can arise from neutron stars in close binary systems. In 1973 the first Gamma Ray Burst was announced. At first it was thought these were just a variation of the X-Ray burst that can arise from neutron stars in close binary systems.

31. Afterglow: hypernova