PROBLEM SET #1, ASTR 451/551
due in class Tuesday, September 16, 2008
1. Chapter 1, problem 1 of Collins
2. Chapter 1, problem 2 of Collins. Also calculate W333/WT O T
for MB, FD and BE.
3. In the following assume the visual magnitude of the Sun as
seen from the Earth is −26.5, and the observed color index of
the Sun is (B−V)= 0.60.
(a) You observe a star with a spectrum that appears to be iden-
tical to that of the Sun. The star has an observed visual mag-
nitude mV= 14. How far away is the star (in parsecs [pc])
assuming there is no dust along the line of sight?
(b) Someone later observes that the color of the star is B−V =
1.10. Recalculate the distance assuming a standard extinction
law with R = 3.1.
(c) What would you expect the J magnitude of this star to be?
You will need to look up the intrinsic colors of a G2 V star
somewhere, for example, Kenyon & Hartmann 1995, ApJS 101,
117. If the J-magnitude turned out to be brighter than expected,
what explanation might you put forward?
(d) Oops. Now a new observation shows that in fact the star
is a double-lined spectroscopic binary, with both components
having identical spectral types. The half-amplitude of the radial
velocity curves is 20 km/s for each component, and the period
is 25 days. Find the inclination of the orbit (0 degrees means
