Kinematic properties and density structure of average Be star envelopes derived from Fe II emission line analysis.
Abstract
In an attempt to derive the velocity and density structure of Be star envelopes, optically thin kinematically broadened emission lines from a cylindric disklike envelope are calculated and fitted to observed high-resolution Fe II emission-line profiles of 16 Be stars. Based on earlier work, kinematic broadening by rotation is investigated; the study is then extended to a simple expansion velocity law and to a combination of rotation and expansion. It is shown that double-peak (so-called class 1) emission-line profiles can be essentially explained by kinematic conditions where rotation dominates and only very slow radial motions are present. Density is found to fall off more rapidly than 1/r sq for more than 50 percent of class 1 profiles and less rapidly for the rest. Class 2 profiles, characterized by a single or a dominating peak, are supposed to originate in elliptical rather than circular disks, with eccentricities in the range e = 0.3 to 0.5. Several mechanisms for the origin of these disks are discussed.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1988
- Bibcode:
- 1988A&A...190..187H
- Keywords:
-
- B Stars;
- Iron;
- Spectral Line Width;
- Stellar Envelopes;
- Stellar Spectra;
- Density Distribution;
- Emission Spectra;
- Thermodynamic Equilibrium;
- Astrophysics