Broad Hα wings from the optically thin stellar wind of the hot components in symbiotic binaries

Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovakia e-mail: skopal@ta3.sk

Received: 30 January 2006
Accepted: 10 July 2006

Abstract

Aims.To model broad Hα 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 Lyβ photons on atomic hydrogen.

Methods.Profile-fitting analysis. Comparison of the observed broad Hα  wings and their luminosity with those predicted by the model.

Results.Synthetic Hα profiles fit excellently the observed wings for  200 km s^-1 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 , 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 Hα-emission, its relationship with the emission measure of the symbiotic nebula and a steep radio spectrum at 1.4–15 GHz suggest the ionized stellar wind from the hot component to be the dominant source contributing to the Hα wings during active phases. The model corresponding mass-loss rates from the hot components are of a few   and of a few   during quiescent and active phases, respectively.