Excitation of gravity modes in white dwarfs with chemically stratified envelopes
Abstract
The vibrational instability of white dwarf models is investigated, taking into account effects of gravitational separation of elements. It is pointed out that the models consist of a carbon core, helium zone, and hydrogen outer layer separated by transition regions, the abundance profile being determined by the diffusion equilibrium. It is found that in the range of effective temperatures corresponding to the observed range for ZZ Ceti stars, the models are unstable against gravity modes when the total mass of hydrogen is less than approximately 1.2 x 10 to the -13 solar mass. The unstable modes are found to correspond to low order spherical harmonics in the period range 100-1200 sec.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1981
- Bibcode:
- 1981A&A....97...16D
- Keywords:
-
- Stellar Envelopes;
- Stellar Gravitation;
- Stellar Models;
- Stellar Oscillations;
- Variable Stars;
- White Dwarf Stars;
- Abundance;
- Carbon;
- Chemical Elements;
- Gravitational Effects;
- Helium;
- Hydrogen;
- Spherical Harmonics;
- Stellar Temperature;
- Astrophysics