Circumstellar dust in Mira variables and the mass loss mechanisms.
Abstract
IRAS data on 92 oxygen-rich Mira variables are analysed to evaluate the role of pulsations in mass loss among these stars. Using a radiative model, equilibrium temperature, size, mass, and optical depth of circumstellar dust shells have been estimated. A two-component dust shell model was found necessary for fitting the photometric data. The LRS data required only a single shell which agrees very well with the inner hotter shell obtained from the photometric data. The mass of the inner shell shows a positive correlation with the pulsation period while that of the outer shell shows no such correlation. We suggest that the outer shell is a result of the mass loss during the pre-AGB stage while the inner shell represents AGB mass loss caused by pulsation with the possible support of radiation pressure. Dust was estimated to condense at ∼3-10R* lending support to the two-step process of mass loss involving the pulsations and radiation pressure. The recently reported variability of far infrared fluxes during pulsation period does not seem to alter these results significantly.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1993
- Bibcode:
- 1993A&A...273..570A
- Keywords:
-
- catalogs: IRAS;
- circumstellar matter;
- stars: mass loss;
- stars: asymptotic giant branch;
- dust;
- stars: infrared