Broad H-alpha wings from the optically thin stellar wind of the hot components in symbiotic binaries

Abstract

Aims: To model broad H-alpha wings observed in symbiotic binaries by an optically thin, bipolar stellar wind from their hot components as an alternative to that considering the Raman scattering of Ly-beta photons on atomic hydrogen. Methods: Profile-fitting analysis. Comparison of the observed broad H-alpha wings and their luminosity with those predicted by the model. Results: Synthetic H-alpha profiles fit excellently the observed wings for |RV| > 200 km/s in our sample of 10 symbiotic stars during the quiescent as well as active phases. The wing profile formed in the stellar wind can be approximated by a function f(RV) proportional to RVexp-2, which is of the same type as that arising from the Raman scattering. Therefore it is not possible to distinguish between these two processes only by modeling the line profile. Some observational characteristics of the H-alpha emission suggest the ionized stellar wind from the hot component to be the dominant source contributing to the H-alpha wings during active phases. The model corresponding mass-loss rates from the hot components are of a few x 10exp(-8) M(Sun)/yr and of a few x (10exp(-7) - 10exp(-6)) M(Sun)/yr during quiescent and active phases, respectively.