Abundances in red giant stars - Nitrogen isotopes in carbon-rich molecular envelopes

Abstract

view Abstract Citations (26) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Abundances in Red Giant Stars: Nitrogen Isotopes in Carbon-rich Molecular Envelopes Wannier, P. G. ; Andersson, B. -G. ; Olofsson, H. ; Ukita, N. ; Young, K. 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. Publication: The Astrophysical Journal Pub Date: October 1991 DOI: 10.1086/170616 Bibcode: 1991ApJ...380..593W Keywords: Abundance; Carbon Stars; Nitrogen Isotopes; Stellar Envelopes; Nuclear Astrophysics; Planetary Nebulae; Silicon Isotopes; Stellar Evolution; Stellar Spectra; Astrophysics; STARS: ABUNDANCES; STARS: CARBON; STARS: CIRCUMSTELLAR SHELLS; STARS: LATE-TYPE full text sources ADS | data products SIMBAD (8)