AST 341 Homework 6

AST 341
Homework 6
Due Friday 7 December 2012
C&O questions are from Carroll & Ostlie, 2nd edition (the big orange book).
1. C&O 14.3
2. C&O 14.8
3. C&O 15.2
4. C&O 15.5
5. C&O 16.14
6. C&O 16.16
7. The optical counterpart of the neutron star Geminga, an X-ray and γ Ray
pulsar, has a V magnitude of 26.5. Its observed surface temperature is 106 K.
A.) What is its distance?
B.) What is its bolometric luminosity? State your answer in solar units.
C.) At what wavelength does the flux peak?
D.) What is the ratio of the X-ray to visual flux? Take the X-rays to be the
flux at 100Å. This ratio can be used to find neutron star candidates.
E.) The pulsar period is 283 msec. If the stellar radius is 10 km, what is the
equatorial rotational velocity?
8. Neutron stars in close binary systems can be heated by accretion from Rochelobe overflow. Assume the mass is 1.5 M⊙ and radius is 10 km.
A.) Show that the luminosity is given by L = GṀM/R where Ṁ is the mass
accretion rate, and M and R are the mass and radius of the neutron star.
B.) What is the Eddington luminosity for this neutron star?
C.) What is the temperature, assuming the photons are thermalized - that is,
the star radiates as a black body?