Multicomponent winds in sdB stars?

In previous diffusion calculations with mass-loss a steady outflow of all elements has been assumed. However, the existence of a chemically homogeneous wind requires an efficient momentum transfer via Coulomb interactions from the heavy elements to hydrogen and helium. For the example T-eff = 35 000 K and log g = 6.0 it will be shown that hydrogen and helium would fall back onto the star if the mass-loss rate is below about 10(-12) M-circle dot/yr. This effect may change the predicted surface compositions.