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12C/13C ratios in giants of open clusters

Published online by Cambridge University Press:  01 August 2006

Rodolfo Smiljanic ,
R. Gauderon ,
P. North ,
B. Barbuy ,
C. Charbonnel  and
N. Mowlavi
Rodolfo Smiljanic
Affiliation:
Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-090, São Paulo SP, Brazil email:rodolfo@astro.iag.usp.brbarbuy@astro.iag.usp.br
R. Gauderon
Affiliation:
Laboratoire d'astrophysique, Ecole Polytechnique Federale de Lausanne (EPFL) – CH 1290 Sauverny, Switzerland
P. North
Affiliation:
Laboratoire d'astrophysique, Ecole Polytechnique Federale de Lausanne (EPFL) – CH 1290 Sauverny, Switzerland
B. Barbuy
Affiliation:
Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-090, São Paulo SP, Brazil email:rodolfo@astro.iag.usp.brbarbuy@astro.iag.usp.br
C. Charbonnel
Affiliation:
Observatoire de Genève 51, Chemin des Maillettes – CH 1290 Sauverny, Switzerland
N. Mowlavi
Affiliation:
Observatoire de Genève - Integral Science Data Center, Chemin d'Ecogia 16 – CH 1290 Versoix, Switzerland
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Abstract

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The carbon isotopic ratio, 12C/13C, is a tracer of the mixing events during the evolution along the giant branch, due to the conversion of 12C into 13C (and 14N) via the CN cycle. A decrease of this ratio from 90, the solar value, to 20–25, is expected due to the first dredge-up. However, ratios down to 3–4, the CN cycle equilibrium value, have been observed in giants of the field, of globular and of open clusters. Observations seem to indicate a non-standard mixing in the RGB, probably beginning in the luminosity bump, when the outward moving hydrogen burning shell crosses the molecular weight barrier left by the convective layer in its maximum extent. We are currently analyzing a sample of 24 giants in 8 open clusters for which we determined 12C/13C from high resolution, high signal to noise spectra using spectrum synthesis. In this work we discuss the general characteristics of our results in comparison to previous analyses of giants in open clusters available in the literature.

Keywords

Stars: abundancesstars: evolutionstars: late-type
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S239: Convection in Astrophysics , August 2006 , pp. 298 - 300
Copyright
Copyright © International Astronomical Union 2007

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