Multi-line analysis of the spectra of Herbig Ae/Be stars

Abstract

We present the results of the study of four Herbig Ae/Be stars (AB Aur, BD+46(deg) 3471, HD250550, BD+61(deg) 154). For each of them, semi-empirical models of the structure of their winds have been constructed; we then calculated the Hα line, the Balmer discontinuity, as well as the C IV 1548 Angstroms and Mg II h or k resonance lines. Thanks to comparison with observational data, we have deduced constraints on the parameters of the models, which provide us with a rather good representation of the averaged structure of the winds. Despite of the time variability of these stars, we show that we can gather trustworthy information on the values of the mass loss rates of these stars. It is also shown that models with departure from spherical symmetry are needed to account for the observed shapes of the lines. In addition, radiative losses due to several transitions (lines and continua) of hydrogen have been evaluated, in order to gain more insight in the energy sources that generate the observed activity of these stars. Based on observations with the Bernard Lyot 2m telescope at Pic du Midi Observatory, France, the archives of the International Ultraviolet Explorer (IUE) collected at the Villafranca Satellite Tracking Station of the European Space Agency, and the archives of the Hubble Space Telescope, collected at the Space Telescope Science Institute in Baltimore.