Singly ionized iron as a diagnostic of stellar envelopes. II The structure of the envelopes of six luminous blue stars.

Abstract

The methods described in Friedjung and Muratorio (1987), involving the self-absorption curve for the Fe II optical emission lines and spectral synthesis for the UV, are applied to study the surroundings of the galactic P Cygni star AG Car and of five luminous Magellanic Cloud stars. Their Fe II emission and absorption spectra are interpreted by line formation in the same isotropic wind. In view of the difficulties encountered using this approach for the Magellanic Cloud stars studied, simultaneous line formation in two different media, are considered and it is concluded that, in those stars, emission lines are most easily understood as formed in a region not in front of the photosphere (probably a dense disk). It does appear that for two of the sample stars (R50 and R82), layers of the disk which are optically thin in the continuum produce the observed Fe II absorption lines, while for two other stars (R66 and S22) the absorption spectrum is due to a wind. In the case of the galactic star AG Car the wind is responsible for the Fe II emission spectrum as well as for the observed Fe II absorption spectrum.