The masses of Wolf-rayet stars.

The masses, mass ratios, and orbital parameters of Wolf-Rayet binaries are discussed. There is no one typical mass for W-R stars, since the known masses range from 10 to 50 solar masses, and span a much larger range in mass than do their O type companions. The average mass of a W-R star is about 20 solar masses. The masses of W-R stars of similar subtypes can be quite different, and there appear to be no systematic connections between the masses and subtypes. The masses of WC stars are not different from the masses of WN stars. Although the mass ratios of W-R binaries are quite different from those of their progenitor O type binaries, the available orbit solutions indicate that the periods are similar. This suggests that orbital angular momentum losses are greater than can be accounted for by either conservative or simplistic wind models. From elementary evolutionary considerations, it appears that the W-R members of binaries have lost at least 40% of their initial mass.