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Atomic and molecular hydrogen in the circumstellar envelopes of late-type starsThe distribution of atomic and molecular hydrogen in the expanding circumstellar envelopes of cool evolved stars is discussed. The main concern is to evaluate the effects of photodestruction of H2 by galactic UV radiation, including shielding of the radiation by H2 itself and by dust in the envelope. One of the most important parameters is the H/H2 ratio which is frozen out in the upper atmosphere of the star. For stars with photospheric temperatures greater than about 2500 K, atmospheric models suggest that the outflowing hydrogen is mainly atomic, whereas cooler stars should be substantially molecular. In the latter case, photodissociation of H2 and heavy molecules contribute to the atomic hydrogen content of the outer envelope. The presented estimates indicate that atomic hydrogen is almost at the limit of detection in the C-rich star IRC + 10216, and may be detectable in warmer stars. Failure to detect it would have important implications for the general understanding of circumstellar envelopes.
Document ID
19830050462
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Glassgold, A. E.
(New York Univ. New York, NY, United States)
Huggins, P. J.
(New York University New York, NY, United States)
Date Acquired
August 11, 2013
Publication Date
May 1, 1983
Publication Information
Publication: Royal Astronomical Society, Monthly Notices
Volume: 203
ISSN: 0035-8711
Subject Category
Astrophysics
Accession Number
83A31680
Funding Number(s)
CONTRACT_GRANT: NGR-33-016-196
Distribution Limits
Public
Copyright
Other

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