A possible interpretation of subgiant delta Scuti variables.
Abstract
The giant Delta Scuti stars with abundance anomalies cannot be explained in the framework of the theory of A stars on the main sequence. The existence of abundance anomalies leads to the idea that they are differentiated stars in which heavy elements have been pushed upward by radiation pressure. In this case helium is bound to be driven downward by gravitation from the outer layers; the helium convection zones disappear and, thus, cannot account for vibrational instability. This paper investigates whether this vibrational instability can be due to the hydrogen ionization zone. A marginal positive result is obtained, and the uncertainties in the physics of the model are discussed.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1979
- Bibcode:
- 1979A&A....73..329V
- Keywords:
-
- Abundance;
- Giant Stars;
- Helium;
- Stellar Models;
- Variable Stars;
- Boundary Value Problems;
- Chemical Composition;
- Hydrogen Ions;
- Radiation Pressure;
- Stellar Envelopes;
- Stellar Gravitation;
- Astronomy;
- A Subgiants:Delta Scuti Stars;
- Delta Scuti Stars:Element Abundances;
- Delta Scuti Stars:Pulsation Theory