The 12C/13C ratio in stellar atmospheres. VI. Five luminous cool stars.
Abstract
A simple curve-of-growth technique is described for extracting the C-12/C-13 ratio for M stars from high-resolution spectra of CO infrared vibration-rotation lines. The technique is applied to the CO lines at 1.6 and 2.3 microns in spectra of two M supergiants (Alpha Ori and Alpha Sco), two M giants (Alpha Her and Beta Peg), and a Mira-type variable (Chi Cyg). As a check on the CO analysis, the C-12/C-13 ratio is derived from the red CN system at 8000 A for Alpha Sco, Alpha Ori, and Beta Peg. The CO analysis is also applied to the K giant Alpha Boo as a check. The CN and CO results are found to be in general agreement, and the C-12/C-13 ratio in all the examined stars is shown to be considerably lower than the solar-system value. It is suggested that these stars were formed from clouds with a C-12/C-13 ratio of 40 to 89 and that their atmospheres now exhibit an enhancement of C-13 abundance due to internal production and mixing to the surface.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1976
- DOI:
- 10.1086/154875
- Bibcode:
- 1976ApJ...210..684H
- Keywords:
-
- Abundance;
- Atmospheric Composition;
- Carbon 12;
- Carbon 13;
- Cool Stars;
- M Stars;
- Stellar Atmospheres;
- Carbon Monoxide;
- Cyanides;
- Giant Stars;
- K Stars;
- Late Stars;
- Mass Ratios;
- Mira Variables;
- Molecular Spectra;
- Supergiant Stars;
- Variable Stars;
- Astrophysics