The intrinsically bright Wolf-Rayet stars of type WN7. I. The binary HD 92740 and the probable single star HD 93131 in Carina.
Abstract
Summary. Photographic coude' spectroscopy and narrow-band photoelectric photometry are used to investigate the nature of these two WN 7 stars-brightest of their kind in the sky. It is shown that HD 92740 is a single-line spectroscopic binary with a period of 80.35 days and a relatively large eccentricity 0.55. Its observed mass function combined with upper mass limits for the unseen secondary and lack of eclipses in the somewhat noisy light curve imply a mass ratio M(WR)/M(secondary) between 0.3 and 1.0. These values overlap with the directly observed ratio (0.2-0.4) in several known WR + OB binaries. The velocities of the relatively weak Balmer absorption lines (H 8- H 10) vary in phase with all remaining lines (emission and absorption) but with less than half their amplitude. This may imply that the Balmer lines of the fainter (late 0-type or early B-type) secondary vary 1800 out of phase with the dominant photo spheric Balmer lines of the WR (and therefore Of-like) primary. The constancy in velocity and light of HD 93131 within the observational precision leads to some restraints as a binary system. If HD 93131 is in fact a normal WR + OB binary, the inclination of the orbit must be 20; conversely, with the most probable inclination of 570, the secondary cannot have a mass more than 3 M0. Such possibilities appear fairly and we may conclude that HD 93131 is more likely to be a true single star. It too has Of4ike Balmer absorption lines indicating that it may have evolved from a single massive Of star by a radiation pressure induced stellar wind. Key words: Wolf-Rayet star - stellar mass loss - spectroscopic binary - individual stars: HD 92740, HD 93131
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1978
- Bibcode:
- 1978A&A....70...69M
- Keywords:
-
- Mass Loss:Wolf-Rayet Stars;
- Masses:Wolf-Rayet Stars;
- Spectrophotometry:Wolf-Rayet Stars;
- Spectroscopic Binaries:Wolf-Rayet Stars