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The C-12/C-13 ratio in stellar atmospheres. V - Twelve K giants and subgiants
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1975
Year
High-resolution photoelectric scans of portions of the CN red system in the spectra of 12 K giants and subgiants have been analyzed for the 12C/13C abundance ratio with the following results: >50 (5 Eri), >30 ( Cep), 51 I 5 (v2 CMa), 24 I 3 (y Cep), 34 I 4 (53 Eri), 16 + 2 (L Cep), 12 I 2(0 Cet), 22 I 2 (A Sgr), 20 I 2 ( Dra), 15 I 2 (p Boo), 18 I 2(5 Sgr), and 25 + 2 (5 And). This sample of stars have relatively low absolute luminosities (log L/L0 < 2.1). Stellar evolution calculations predict that their atmospheres will contain an overabundance of 13C as a result of a convective envelope which has brought to the surface 13C produced in the interior during main-sequence burning. The 13C is observed in all except the two faintest stars. Interpretations of the observed range of results, 5 < 12C/'3C < 55, for giants and subgiants are discussed. Subject headings: abundances, stellar - late-type stars molecules