Spectroscopic studies of O-type stars. VI. The earliest types: O3 - O5.5.
Abstract
We present equivalent widths and selected line profiles obtained from multiple coude' spectrograms of 20 early 0 and Of stars. In the hottest stars, the O3 types, the neutral helium lines are absent, and in the other stars it is essentially the strength of He I A4471 that determines the spectral type. In these early 0-type stars the ionized helium lines are relatively insensitive to temperature and slightly weaker than predicted by the non-LTE models of Auer and Mihalas. The presence of strong emission at Ha and/or He ii A4686 in seven of these stars suggests appreciable mass loss via a stellar wind. Neither of these emission lines nor N iii AA4634, 4640, 4641 exhibited noteworthy variations during the period of observation. The rates of mass loss, as deduced from the formalism of Klein and Castor, are of order l0- yr . These rates are sufficiently large, if continued throughout the hydrogen burning lifetime of the star, to carry away a significant fraction of the mass of the star. Subject headings: line profiles - stars: early-type - stars: mass loss - stars: Of-type
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1977
- DOI:
- 10.1086/155098
- Bibcode:
- 1977ApJ...212..728C
- Keywords:
-
- Early Stars;
- Emission Spectra;
- Line Spectra;
- O Stars;
- Stellar Spectra;
- H Alpha Line;
- Hertzsprung-Russell Diagram;
- Mass Transfer;
- Spectral Line Width;
- Stellar Mass;
- Astronomy