  The birthrate of stars of masses > 10 solar masses is estimated from a sample
of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sun and the result
extrapolated to estimate the galactic supernova rate contributed by such stars.
The solar-neighborhood galactic-plane massive star birthrate is estimated at
176 stars per cubic kpc per million years. Based on a model where the galactic
stellar density distribution comprises a disk plus central hole like that of
the dust infrared emission (Drimmel & Spergel 2001 ApJ 556, 181) the galactic
supernova rate is estimated as probably not less than 1 nor more than 2 per
century and the number of O3-B2 dwarfs within the solar circle as ~ 200,000.
