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Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopesResults are presented of millimeter- and submillimeter-wave observations of HCN and HCCCN that were made of the circmustellar envelopes of eight carbon stars, including the two protoplanetary nebulae CRL 618 and CRL 2688. The observations yield a measure of the double ratio (N-14)(C-13)/(N-15)(C-12). Measured C-12/C-13 ratios are used to estimate the N-14/N-15 abundance ratio, with the resulting lower limits in all eight envelopes and possible direct determinations in two envelopes. The two determinations and four of the remaining six lower limits are found to be in excess of the terrestrial value of N-14/N-15 = 272, indicating an evolution of the nitrogen isotope ratio, which is consistent with stellar CNO processing. Observations of thermal SiO (v = 0, J = 2-1) emission show that the Si-29/Si-28 ratio can be determined in carbon stars, and further observations are indicated.
Document ID
19910072255
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Wannier, P. G.
(JPL Pasadena, CA, United States)
Andersson, B.-G.
(JPL, Pasadena, CA; Goteborg, University Sweden)
Olofsson, H.
(Onsala Space Observatory Sweden)
Ukita, N.
(Nobeyama Radio Observatory Minamimaki, Japan)
Young, K.
(California Institute of Technology Pasadena, United States)
Date Acquired
August 14, 2013
Publication Date
October 20, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 380
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
91A56878
Distribution Limits
Public
Copyright
Other

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