Chemical separation in horizontal-branch stars.
Abstract
Horizontal branch (HB) and halo Population II star abundance anomalies are predicted to arise from diffusion processes, and for cases where the outer envelope is stable enough for the gravitational settling of He to be efficient, it is shown that heavy element overabundances are simultaneously produced. Selective radiative acceleration and abundance time evolution calculations are presented for C, N, O, Ca, Fe, and Sr, in a series of models representative of HB stars. The role of turbulent mixing in the reduction of abundance anomalies is discussed, and it is shown that despite sufficient turbulence to keep He from settling, heavy element abundance anomalies remain possible. While chemical separation is important in the blue HB stars, it may not be in cooler stars where mass loss may be able to eliminate any chemical separation effect.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1983
- DOI:
- 10.1086/160864
- Bibcode:
- 1983ApJ...267..256M
- Keywords:
-
- Abundance;
- Chemical Composition;
- Globular Clusters;
- Helium;
- Horizontal Branch Stars;
- Stellar Models;
- B Stars;
- Big Bang Cosmology;
- Cosmochemistry;
- Stellar Envelopes;
- Strontium;
- Turbulence Effects;
- Astrophysics