The alpha -enhanced Isochrones and Their Impact on the FITS to the Galactic Globular Cluster System
Abstract
The effect produced by the enhancement of the alpha-elements O, Ne, Mg, Si, S, and Ca on the evolutionary properties of low-mass, low-metallicity stars is analyzed, with emphasis on the evolutionary phases which extend from the main sequence up to the H reignition on the AGB. It is found that evolutionary models (suitable for Population II stars) with alpha-enhanced chemical composition can be computed even though proper low-temperature opacities are not yet available, since it is demonstrated that most of the evolutionary properties of Population II stellar models are not influenced by the metal content included in the opacity coefficient below 12,000 K. The fit to Groombridge 1830 is discussed, and it is concluded that it is unnecessary, at present, to revise the value of the mixing-length parameter obtained by fitting the sun.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1993
- DOI:
- 10.1086/173105
- Bibcode:
- 1993ApJ...414..580S
- Keywords:
-
- Globular Clusters;
- Milky Way Galaxy;
- Stellar Evolution;
- Stellar Interiors;
- Stellar Models;
- Asymptotic Giant Branch Stars;
- Luminosity;
- Main Sequence Stars;
- Metallicity;
- Opacity;
- Stellar Composition;
- Astrophysics;
- GALAXY: GLOBULAR CLUSTERS: GENERAL;
- STARS: ABUNDANCES;
- STARS: EVOLUTION;
- STARS: INTERIORS