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Title:
Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes
Authors:
Wannier, P. G.; Andersson, B.-G.; Olofsson, H.; Ukita, N.; Young, K.
Affiliation:
AA(JPL, Pasadena, CA), AB(JPL, Pasadena, CA; Goteborg, University, Sweden), AC(Onsala Space Observatory, Sweden), AD(Nobeyama Radio Observatory, Minamimaki, Japan), AE(California Institute of Technology, Pasadena)
Publication:
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 380, Oct. 20, 1991, p. 593-605. (ApJ Homepage)
Publication Date:
10/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ABUNDANCE, CARBON STARS, NITROGEN ISOTOPES, STELLAR ENVELOPES, NUCLEAR ASTROPHYSICS, PLANETARY NEBULAE, SILICON ISOTOPES, STELLAR EVOLUTION, STELLAR SPECTRA
DOI:
10.1086/170616
Bibliographic Code:
1991ApJ...380..593W

Abstract

Results 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.

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