Probing the AGB tip : luminous carbon stars in the galactic plane.
Abstract
To address the question of the progenitor mass range of carbon stars, we searched for CO emission from a sample of distant (d ∼ 2-10 kpc), heavily obscured asymptotic giant branch (AGB) stars that are confined to the galactic plane. We detected 47 stars for the first time, and have determined luminosities for ∼40 of these via a kinematic technique. Based on IRAS low resolution spectra, detections of circumstellar molecules other than CO, IR colors, and/or CO line strength relative to IRAS flux, we have classified the bulk of the circumstellar envelopes as carbon- or oxygen-rich. We deduce similar average luminosities for carbon stars and oxygen-rich stars from 1.3 104 to 2 1O4 Lsun, depending on the method used to compute bolometric fluxes. These averages are larger than typically assumed or derived for carbon stars in the solar neighborhood, and are similar to the average luminosity of "cold" OH/IR stars. The results suggest that luminous carbon and oxygen-rich AGB stars near the galactic plane are descended from stellar populations of similar mean mass. This mean mass (>2Msun) is probably larger than the mean progenitor mass of AGB stars in general.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1993
- Bibcode:
- 1993A&A...275..163K
- Keywords:
-
- surveys;
- stars: carbon;
- stars: AGB;
- stars: evolution;
- circumstellar matter;
- radio lines: stars