CNO Abundances and the Evolutionary Status of Three A-Type Supergiants
Abstract
The study presents results for three massive (about 10-solar masses), Population I A-type supergiants: HD 13476 (A3 Iab), HD 46300 (A0 Ib), and HD 87737 (A0 Ib). Atmospheric parameters (T(eff) and gravity) are determined from spectroscopic indicators. Observed H-gamma profiles are compared to those generated from Kurucz's (1979, 1990) line-blanketed model atmospheres, and ionization equilibrium of MgI/Mg II is used to choose the final model parameters. These A supergiants are found to have roughly solar metal abundances. There are large enrichments of nitrogen, accompanied by slight carbon and possibly oxygen depletions. The nitrogen enhancements indicate a complex chemical evolutionary history for the stars, or a systematic error in the classical analysis of N I lines in A supergiant atmospheres, e.g., large non-LTE corrections.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1993
- DOI:
- 10.1086/173078
- Bibcode:
- 1993ApJ...414..316V
- Keywords:
-
- A Stars;
- Cyano Compounds;
- Oxygen Compounds;
- Stellar Evolution;
- Stellar Interiors;
- Supergiant Stars;
- Abundance;
- Charge Coupled Devices;
- Massive Stars;
- Signal To Noise Ratios;
- Astrophysics;
- STARS: ABUNDANCES;
- STARS: EVOLUTION;
- STARS: INTERIORS;
- STARS: SUPERGIANTS