Obscured Asymptotic Giant Branch stars in the Magellanic Clouds. IV. Carbon stars and OH/IR stars
Abstract
We present N-band photometry for a sample of 21 dust-enshrouded AGB stars in the Large Magellanic Cloud, and three additional sources in the Small Magellanic Cloud. Together with near-infrared photometry, this is used to give a tentative classification into carbon and oxygen-rich atmospheres. Bolometric luminosities are also estimated for these stars. In addition, we present the results of a survey for OH masers in the LMC, which resulted in the discovery of OH maser emission from IRAS04407-7000. Spectra between 600 and 1000 nm have been obtained for two heavily obscured AGB stars in the LMC, confirming them to be highly reddened very late M-type giants. Because the dust-enshrouded stars are clearly undergoing heavy mass loss they are assumed to be very near the termination of their respective Asymptotic Giant Branch phases. The fraction of mass-losing carbon stars decreases with increasing luminosity, as expected from Hot Bottom Burning. The best candidate carbon star, with M_bol ~ -6.8 mag, is the most luminous mass-losing carbon star in the Magellanic Clouds, and amongst the most luminous AGB stars. At lower luminosities (M_bol ~ -5 mag) both oxygen and carbon stars are found. This may be explained by a range in metallicity of the individual mass-losing AGB stars. based on observations obtained at the European Southern Observatory (La Silla, Chile: proposal ESO 54.E-0135), the South African Astronomical Observatory, and the Australia Telescope National Facility
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1998
- DOI:
- 10.48550/arXiv.astro-ph/9709119
- arXiv:
- arXiv:astro-ph/9709119
- Bibcode:
- 1998A&A...329..169V
- Keywords:
-
- STARS: CARBON;
- CIRCUMSTELLAR MATTER;
- STARS: MASS LOSS;
- STARS: AGB AND POST-AGB;
- MAGELLANIC CLOUDS;
- INFRARED: STARS;
- Astrophysics
- E-Print:
- 17 pages, with 8 figures. Accepted by Astronomy and Astrophysics, Main Journal