Mass loss predictions for Subdwarf B stars

Abstract

We present the results of Monte Carlo mass-loss predictions for hot low-mass stars, specifically for Subdwarf B (SdB) stars. It is shown that the mass-loss rates on the Horizontal Branch (HB) computed from radiative line-driven wind models are not high enough to create SdB stars. We argue, however, that the mass loss plays a role in the chemical abundance patterns observed both in field SdB stars, as well as in cluster HB stars. The derived mass loss recipe for these (extremely) hot HB stars may also be applied to other groups of hot low-mass stars, such as post-HB (AGB-manque, UV-bright) stars, over a range in effective temperatures between 10000 and 50000 Kelvin. Finally, we present preliminary spectral synthesis on the more luminous SdB stars for which emission cores in Halpha have been detected (Heber et al. 2002). We find that these line profiles can indeed be interpreted as the presence for a stellar wind with mass loss of the order of log(Mdot) = -11 (Msun/year).