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Al-26 and circumstellar envelopesThe effects of the radioactive decay of Al-26 on the circumstellar envelopes of asymptotic giant branch stars are analyzed. The gamma-rays emitted by the product nucleus Mg-26 escape most envelopes, but the beta-decay positrons are stopped and can ionize and heat the gas. The ionization may produce observable effects in C-rich circumstellar envelopes, particularly if the photospheric Al-26 abundance is as large as inferred from measurements of live Al-26 in the primitive solar nebula or the observations of interstellar 1.8 MeV gamma-rays. For the nearby carbon star IRC +10216, the measured abundance of the molecular ion HCO(+) provides an upper limit of about 4 x 10(exp -3) for the photospheric Al-26/Al-27 ratio, consistent with presolar SiC grains with about the same C-12/C-13 ratio.
Document ID
19950037971
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Glassgold, A. E.
(New York Univ. New York, NY, United States)
Date Acquired
August 16, 2013
Publication Date
January 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 438
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
95A69570
Distribution Limits
Public
Copyright
Other

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