1995A&A...301..823B

The multicomponent nature of the wind is a fundamental aspect of the wind of A and B stars. We first show that a radiatively driven wind can exist on main sequence A stars only if the wind is inhomogeneous. Using a multifluid approach, we present a model for radiatively driven winds on these objects. A detailed numerical simulation is performed for an A star, with T_eff=10000K, on the ZAMS. We solve in a self-consistent way for the mass loss rate, for the energy balance in the wind and for the photospheric abundances. We obtain that only minor elements are expelled from the star and that H and He remain bound to the star. The mass loss rates obtained are very small, lower than {dot}(M)=10^–16M_☉/yr but of metals only. These rates are in agreement with the existence of abundance anomalies on chemically peculiar (Cp) stars. The mass loss rate depends crucially on whether or not chemical separation occurs in the photosphere. This result indicates an interesting possible difference between normal A and Ap stars.
Result. are also obtained for the abundance of metals in the photosphere and could give a key to abundance anomalies on Cp stars. Another important point is on the energy balance of the wind. Our computations show that even on A stars, frictional heating is a major effect which could substantially heat the plasma and create UV or EUV excesses from these objects.