Molecular abundances in stellar atmospheres. II.
Abstract
Summary. Chemical equilibria of 36 elements are solved for the physical conditions of cool stellar atmospheres. It is found that the molecular species formed (monoxide, dioxide, halide etc.) and the degree of molecular association, (i. e. the fraction of atoms locked in molecules) are well correlated with the position of each element (both Group and atomic weight) in the periodic table. In the atmospheres of carbon-rich stars, molecular formation is generally less important than in oxygen- rich atmospheres except for some carbon compounds. The metal oxides in oxygen-rich atmospheres are generally replaced by metal carbides, especially by dicarbides, in carbon-rich atmospheres. The formation of carbides in carbon-rich atmospheres, however, is less effective than that of the corresponding metal oxides in oxygen-rich atmospheres. In carbon stars, it is shown that the Si/S ratio plays a critical role just like the C/O ratio. Key words: equilibrium constants - chemical equilibrium - molecular abundance - atmospheres of cool stars
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1973
- Bibcode:
- 1973A&A....23..411T