Stellar wind signatures in sdB stars?

Abstract

Subdwarf B (sdB) stars form the blue end of the horizonal branch. Their peculiar atmospheric abundance patterns are due to diffusion processes. However, diffusion models fail to explain these anomalies quantitatively. From a NLTE model atmosphere analysis of 40 sdB stars, we found that the more luminous (i.e. more evolved) stars have anomalous H alpha and HeI 6678Ang line profiles, i.e, the lines are too broad and shallow and may even show some emission. We interpret these anomalies as the signatures of a stellar wind, the first such detection in this class of star (if confirmed). Mass loss may also explain the peculiar abundance patterns seen in sdB stars. High-quality UV spectra are needed to confirm that these stars do have stellar winds.