A study of UV spectra of zeta Aur/VV CEP stars. X. Mass-loss of alphaSco A from high-resolution IUE spectra of alpha SCO B.

Abstract

We redetermine the rate of mass-loss of the M super- giant α Sco by means of circumstellar lines observed with IUE in the ultraviolet spectrum of its B star companion. We first show 1) that nearly all UV lines, on which previous mass-loss determinations (v.d. Hucht et al., 1978; Bernat, 1982) were based, are blends with interstellar lines and 2) that the remaining 'pure' circumstellar lines have P Cyg profiles for which radiative transfer had been treated incorrectly. This explains both the discrepancy between mass-loss rates from UV lines and optical Ti II lines (Kudritzki and Reimers, 1978) and the large scatter (factor 30) among rates from individual ions (Bernat, 1982). By application of correct line transfer calculations to P Cyg type lines of Si II, O I and Fe II and Ti II (optical) lines we a mass-loss rate of ∼ 1× 10^-6 M_sun/yr with an uncertainty of a factor of at least 2 either way, in excellent agreement with the values from optical lines (Kudritzki and Reimers, 1978) and from radio emission of the H II region (Hjellming and Newell, 1983).