H and He II spectra of Of stars

the dynamical models of Of stars developed in a previous publication are used as the basis of a set of statistical equilibrium calculations for hydrogen and ionized helium, on the hypothesis of radiative equilibrium in the stellar envleope. A number of spectral lines of these species are observed in the expanding envelopes of Of stars, and thus they provide diagnostic information about the stellar wind. It is found that the Hα line has a strength that is quite sensitive to the rate of mass loss by the star, and comparison with observation indicates loss rates as high as 10-5M/sub sun/ yr-1. The ratio Hα/He II lambda4686 as observed is in agreement with one of the two sets of theoretical values that are computed; the choice is allowed by uncertainties in the treatment of He II lambda304. Other lines of He II, for which the data are more fragmentary, give only factor-of-2 agreement with theory. The computed profiles of Hα and lambda4686 are in qualitative agreement with observation, but certain systematic differences exist: the effect of absorption on the violet side of the emission profile is generally more marked in the theoretical profile. The effect of assuming a higher electron temperature in the stellar wind is considered. The primary change would be an upward adjustment in the inferred rates of mass loss, with some worsening of agreement between theory and observation of the Hα/lambda4686 ratio in the later subclasses