Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1981
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981ap%26ss..75..341j&link_type=abstract
Astrophysics and Space Science, vol. 75, no. 2, Apr. 1981, p. 341-351.
Astronomy and Astrophysics
Astrophysics
1
Chemical Reactions, Interstellar Chemistry, Reaction Kinetics, Stellar Envelopes, Abundance, Giant Stars, Molecular Clouds, Stellar Mass Ejection, Time Dependence
Scientific paper
The rate equations of a restricted set of gas-phase chemical reactions occuring in an expanding circumstellar envelope are integrated numerically on the assumption that no chemical evolution has occurred in the stellar atmosphere. Abundances of all species are found to peak at a time on the order of the ratio of the initial radius to the expansion velocity. After this time geometrical dilution dominates. For an initial density of 10 to the 8th/cu cm, on the order of 1% of hydrogen is converted to H2, and CH and CO have comparable densities of approximately 10 to the -6th relative to H; OH and O2 remain very low in abundance. For higher initial densities, H and H2 are more nearly comparable, and nearly all carbon is in CO, CH; OH and OH and O2 remain low in abundance. The relevance of these results to M giants and other objects is discussed.
Jameson P. V.
Williams David. A.
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