Carbon stars and circumstellar shells. III. Inferences on stellar data.
Abstract
An effective temperature scale for cool carbon stars is proposed on the basis of analyses of spectral energy curves. It is shown that the calibration of Mendoza and Johnson (1965) should be corrected for contamination of the K magnitude by shell emission and that their photometric index, inferred from cool oxygen stars, should be replaced. Effective temperatures, variability, and periods are analyzed for both Mira and 'non-Mira' variables, angular diameters are derived, and the problem of determining distances is discussed. Carbon abundances are investigated qualitatively, and it is argued that non-Miras with shells populate a sequence where carbon abundance increases as effective temperature decreases. Using the Cij classification of Keenan and Morgan (1941), non-Miras with shells are classified as C4 through C7, the coolest stars of the sample are classified as C3 through C5 because of strong CN blanketing, and the hottest stars are classified as C7.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1976
- Bibcode:
- 1976A&A....52..263B
- Keywords:
-
- Astronomical Catalogs;
- Carbon Stars;
- Stellar Envelopes;
- Stellar Temperature;
- Abundance;
- Mira Variables;
- Stellar Models;
- Variable Stars;
- Astrophysics