Stellar Wind Signatures in sdB Stars

Abstract

Subdwarf B (sdB) stars form the blue end of the horizontal branch. Their peculiar atmospheric-abundance patters result from 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 Ha and He I6678A 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 see in sdB stars. High-quality UV spectra are needed to confirm that these stars do have stellar winds.