Brian Skiff from the Lowell Observatory posted this information on another web site which I thought would be of interest
Re: [amastro] Sirius B in the Lowell Clark refractor
I did some poking around in the literature to find current
'best' values for the V magnitudes of Sirius A and B. Alan Cousins
surely measured Sirius with the most care, and his V = -1.43.
A recent spectrophotometric observation of Sirius B using HST
yields V = 8.53 (
http://arxiv.org/abs/astro-ph/0506600) with
quite small uncertainty. Its current orbital position places it
8".5 from Sirius in pa 94 degrees.
Some other interesting numbers come from another recent study
by Jim Liebert and gang (
http://arxiv.org/abs/astro-ph/0507523).
They find the white dwarf progenitor started out at 5 solar masses,
so it would have been a luminous B-type star a couple hundred
million years ago (Sirius is close to 2 solar masses), and of course
would have outshone Sirius (which would have been the "companion").
The white dwarf is now down to something close to 1.0 solar mass,
and the paper cited in the first paragraph estimates the diameter
as 0.0081 solar, call it 11,000 km = 7000 miles, so a bit smaller
than the diameter of Earth.
\Brian
