White dwarf Sirius BSirius binary at 2.6 pcOrbital period: 50.1 y

Sirius AM = 2.1 Msun-star (main seq.)Teff = 9900 KL = 25.4 LsunR à 1.7 Rsun

Sirius BM = 1.0 Msun - white dwarfTeff = 25'000 KL = 0.027 LsunR à 0.0086 Rsun

R follows from: L=4πR2σT4

Astrophysics I, Lecture Slides – Chapter 6, ETH Zurich

1

Mass-radius relation for white dwarfs

≈ 0.01 Rsun

2

Regions in the density – temperature diagram

from Choudhuri

Indicated:- center of the sun: - run of parameters from center towards surface (dashed line)

3

Nuclear burning regions in the ρ – T diagram

Indicated in red:- location of

central stellar parameters for different nuclear burning stages

p-p

CNO 3α

C+C

Si-burn.O+O

4

Evolution of stars in ρ – T diagram

Indicated in blue:evolution of central parameters for- planets - low mass stars- sun- high mass stars

p-p

CNO 3α

C+C

Si-burn.O+O

~0.01 Msun

~0.2 Msun

~1 Msun

~20 Msun

5

6

Pulsar signals

7from Choudhuri

Pulsar period glitches

8from Choudhuri

Pulsar statistics

9from Choudhuri

Mass transfer in binaries

10from Choudhuri

Mass estimates for nutron stars

11from Choudhuri