Criteria for OH maser emission from circumstellar envelopes of oxygen-rich Mira-type red giants.
Abstract
A large and representative sample of oxygen-rich Mira stars was selected and observed in the 18 cm OH lines at their optical maximum. A total of 14 new OH sources were detected. The OH maser emission is found in the intrinsically bright far-IR objects with late M spectral type. Other characteristics of the Miras are high (H-K) and (K-L) colors. Their periods are on average longer and their (25-12) colors on average redder than those of non-OH Miras. The (J-H) and (60-25) colors are the same for OH and non-OH stars. In most cases, OH and H2O masers exist simultaneously. The observed stars form a sequence along which the period and the stellar luminosity increase, the stellar radius increases, the dust shell radius increases by a smaller factor, the photospheric temperature decreases but the dust shell temperature is roughly constant, and the mass loss rate and thus the thickness and the brighntess of the envelope increase considerably.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1988
- Bibcode:
- 1988A&A...206..285S
- Keywords:
-
- Hydroxyl Emission;
- Mira Variables;
- Red Giant Stars;
- Stellar Envelopes;
- Water Masers;
- Asymptotic Giant Branch Stars;
- Infrared Astronomy Satellite;
- M Stars;
- Stellar Color;
- Stellar Evolution;
- Stellar Spectrophotometry;
- Astrophysics