Grain-gas interaction in envelopes of red giants.
Abstract
A model for red-giant dust-shell ejection is considered in which a cloud of spherical silicate grains expands through an expanding gaseous stellar envelope that is indirectly accelerated by stellar radiation pressure. The model equations are developed with emphasis on the hydrodynamic aspect of the problem, and silicate efficiency factors for radiation pressure are evaluated. The equations are solved numerically as an initial-value problem using a Runge-Kutta approach, and results are presented for grain sizes of 100, 500, and 1000 A. These results verify that the mechanism of mass ejection by the indirect action of stellar radiation pressure through a circumstellar dust shell works for cool giant stars and indicate that gas molecules constitute most of the mass loss. An expression is given for estimating the rate of grain ejection into interstellar space, and it is concluded that the contribution of red giants to interstellar dust clouds is probably small.
- Publication:
-
Revista Brasileira de Fisica
- Pub Date:
- December 1976
- Bibcode:
- 1976RBrFi...6..459M
- Keywords:
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- Red Giant Stars;
- Stellar Envelopes;
- Stellar Mass Ejection;
- Stellar Models;
- Boundary Value Problems;
- Radiation Pressure;
- Runge-Kutta Method;
- Silicates;
- Stellar Radiation;
- Astrophysics