Homework #6
Q2.  Spectroscopic parallax.  (Apparent)
magnitude = 5.4 for an O6 V star.  How far
away is it?  First need to get an absolute
magnitude.  Can estimate it several ways
(H-R diagrams, mass-luminosity relation).  I
used M = -5.6.  So:
d (pc) = 10 (m-M+5)/5 = 103.2 = 1585 parsecs