The Wolf-Rayet binary theta Muscae.
Abstract
Summary. Photographic coude' spectroscopy, narrow- band photoelectric photometry and rapid scanner spectrophotometry are used to analyse the bright WolfRayet binary 0 Muscae (WC 6+09.5/B 0 lab). The emission lines vary in velocity with period P= 18.341+0.008 days (or possibly 18.596 or 18.858 days). The C iv 5801/12 emission feature yields the amplitude K(WR) = 173 km s . The broad C iii 5696 line is phase shifted by C. 1/4 P and varies with amplitude 493 km s . The strength of the C iv 4658 feature varies in a double wave, C iii 4651 in a single (larger) wave. These facts are combined to derive a qualitative model for the WR component with strong streaming motion of the outer (C iii) layers of the envelope and some, but much less distortion of the inner (C iv) layers. The 0-star component has virtually constant velocity (-0.8+1.4 km - 1 during 1970/71). An upper (3a) limit for the velocity amplitude K(O) <6 km s - leads to an exceptionally large mass ratio for 0 Mus as a double system in which large mass loss from the WR component must have occured. The mass ratio can be normalized by postulating a third close, unseen companion (Sp > late 0 V) which orbits the WR star, leaving the observed 0-type star in a wider, slower orbit. Previous published velocities of the 0-type star lend support to this conclusion. Key words: Wolf-Rayet star spectroscopic binary 0 Muscae
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1977
- Bibcode:
- 1977A&A....54..607M