SIMBAD references

In the theory of radiation-driven winds by Castor et al. (1975) (hereafter CAK), the radiative acceleration has no formal dependence on the outwards velocity in the wind and the detailed shadowing by photospheric lines is not included in the computation of radiative accelerations (or force multipliers). In this paper, we compute radiative accelerations taking this effect into account and show that the detailed shadowing by photospheric lines has large consequences on the wind of main sequence B stars. Using these computations, we reconsider the onset and the existence of winds in B stars. In particular, a criterion based on the sonic point of the wind permits to define three zones in the HR diagram where (i) only negligible radiatively driven winds are possible, (ii) only inhomogeneous winds can exist and (iii) where homogeneous winds can be present. These zones are very different from the ones found by Abbott (1979). They are in very good agreement with the locus of chemically peculiar stars, and in particular with He-weak, ³He and He-rich stars. We also incorporate the effect of detailed photospheric shadowing in computations of wind models for stars in which homogeneous wind solutions may exist. The main difference from the CAK theory is found in main sequence B stars, typically for stars with T_eff≃20000-23000K and logg≃3.7-4.0. This gravity is within a factor of 0.25-1.0 of the gravity for which only inhomogeneous winds are possible. For these objects, the mass loss rate is found to be lower than predicted by CAK theory by at least a factor of 4. We also obtain an anticorrelation between the mass loss rate and the ratio u_∞/u_esc with values of u_∞/u_esc, which in some cases exceed 4.