Near-infrared spectroscopy of gamma Cassiopeiae : constraints on the velocity field in the envelope.
Abstract
Spectroscopy of the bright Be star Gamma Cas in the IR lines of hydrogen (Paschen-beta, Paschen-gamma and Brackett-gamma) and helium (10830 and 20581 A) is reported. The resolution was approximately 1 wavenumber. All lines are well resolved. They show profiles of two kinds: Br-gamma and He I 20581 A lines are double-peaked, with maxima of about equal intensity, while Pa-beta and He I 10830 A lines have asymmetric profiles, exhibiting well only one maximum. The analysis of the line profiles implies that, in the epoch of the observations, the velocity of the outflow in the inner layers of the envelope (closer than about 3 stellar radii) did not exceed 90 km/s, but at larger distances the velocity was certainly higher. The new constraints on the velocity field are compared with models of Be stars; the comparison leads to the conclusion that the radiatively driven wind model of Castor et al. (1975) does not apply to Gamma Cas.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1985
- DOI:
- 10.1086/163332
- Bibcode:
- 1985ApJ...294..640C
- Keywords:
-
- B Stars;
- Infrared Astronomy;
- Near Infrared Radiation;
- Stellar Envelopes;
- Stellar Spectra;
- Variable Stars;
- Helium;
- Hydrogen;
- Paschen Series;
- Velocity Distribution;
- Astrophysics