High mass-loss carbon stars and the evolution of the local 12C/13C ratio

Jane Sophia Greaves, WS Holland

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

The C-12/C-13 ratio has been measured in a sample of 10 carbon stars with high mass-loss rates, of greater than or equal to 10(-5) M-. yr(-1). This sample is complete for northern hemisphere carbon stars within similar to 1 kpc of the Sun. Using the J=2-1 rotational lines of CO and (CO)-C-13, the intensity ratio of (CO)-C-12/(CO)-C-13 is found to be 17 +/- 11 for the sample, and the deduced C-12/C-13 abundance ratio, after corrections for CO optical depth effects, is 25 +/- 13. The isotopic ratios are rather uniform (12-36 for 9 of the 10 stars), and there are no stars with very low C-12/C-13 values, such as the ratios of 3-4 found for a few low mass-loss carbon stars.

The ejecta from the high mass-loss objects will dominate the evolution of the C-12/C-13 ratio in the local interstellar medium, since mass return is dominated by AGB stars, and the stars of the highest M return the majority of the carbon. Thus the ejection of C-13-rich material from AGB stars could explain the evolution of the local C-12/C-13 ratio from 89 at the time of the Sun's formation, to 60-70 now. From our data, it is estimated that the local ISM ratio should have evolved to approximate to 72 +/- 8 at the present time, which agrees with ISM observations. The AGB stars can therefore fully explain the enrichment of the local ISM in C-13.

Original languageEnglish
Pages (from-to)342-348
Number of pages7
JournalAstronomy & Astrophysics
Volume327
Publication statusPublished - Nov 1997

Keywords

  • ISM: abundances
  • ISM: clouds
  • CIRCUMSTELLAR ENVELOPES
  • EVOLVED STARS
  • LOSS RATES
  • INTERSTELLAR-MEDIUM
  • SOLAR NEIGHBORHOOD
  • OXYGEN ISOTOPES
  • CO
  • EMISSION
  • ABUNDANCES
  • LINES

Fingerprint

Dive into the research topics of 'High mass-loss carbon stars and the evolution of the local 12C/13C ratio'. Together they form a unique fingerprint.

Cite this