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C,N and key heavy elements in metal-poor and very metal-poor carbon-enhanced stars

Published online by Cambridge University Press:  23 December 2005

T. Masseron
Affiliation:
GRAAL, Université Montpellier II, 34095 Montpellier cedex 5, France email: masseron@graal.univ-montp2.fr
B. Plez
Affiliation:
GRAAL, Université Montpellier II, 34095 Montpellier cedex 5, France email: masseron@graal.univ-montp2.fr
F. Primas
Affiliation:
European Southern Observatory (ESO), Karl-Schwarschild-Str. 2, 85749 Garching b. München, Germany
S. Van Eck
Affiliation:
Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
A. Jorissen
Affiliation:
Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
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Abstract

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A new class of carbon-rich stars was revealed by large surveys of very metal-poor objects, the carbon-enhanced metal-poor stars (CEMPs). This carbon enhancement is reminiscent of that found in classical CH stars, which despite being halo stars, are not as metal-poor as CEMPs. Although a mass-transfer scenario similar to that formerly at work in CH stars could account for the abundance pattern of CEMPs, differences arise for some key heavy elements. Moreover, statistical studies find 14%; of metal-poor C-rich stars among very metal-poor stars. Thus, this important population of stars represents a precious testimony for nucleosynthesis and chemical evolution at early stages of the Galaxy. We have started a detailed analysis of a large sample of both CH and metal-poor C-rich stars. Here we present results concerning the chemical composition obtained via high resolution and high signal-to-noise VLT-UVES spectra, with special emphasis on the challenges encountered during the abundance analysis. The discussion also includes preliminary results of our ongoing radial velocity monitoring programme which aims at evaluating the relevance of the binary scenario.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union