Kinematical structure of the circumstellar environments of galactic B[e]-type stars

Abstract

High resolution line profiles are presented for selected forbidden and permitted emission lines of a sample of galactic B[e]-type stars. The spectral resolution corresponds to 5-7 km/s with the exception of some line profiles which were observed with a resolution of 9-13 km/s. All Ha profiles are characterized by a narrow split or single emission component with a width of about 150-250 km/s (FWHM) and broad wings with a full width of ~1000-2000 km/s. The Ha profiles can be classified into three groups: double-peaked profiles representing the majority, single-peaked emission-line profiles, and normal P Cygni-type profiles. The forbidden lines exhibit in most cases double-peaked profiles. The split forbidden line profiles have peak separations of as little as 10 km/s. The ratio of violet to red emission peak intensities, V/R, is predominantly smaller or equal to 1. Theoretical profiles were calculated for the optically thin case. A latitude-dependent stellar wind with a radial expansion and a velocity decreasing from the pole to the equator was adopted. In addition an equatorial dust ring with various optical depths was assumed. This model can explain split lines and line asymmetries observed in some stars. Moreover, the V/R ratios can be understood in terms of this model. The comparison of the observed line profiles with the models thus confirms the assumption of disk-like line-formation regions as commonly adopted for B[e]-type stars.