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What helium and lithium can tell us about CEMP stars?

Published online by Cambridge University Press:  23 April 2010

Georges Meynet
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
Raphael Hirschi
Affiliation:
Astrophysics group, Keele University, Lennard-Jones Lab., Keele, ST5 5BG, UK IPMU, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
Sylvia Ekstrom
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
André Maeder
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
Cyril Georgy
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
Patrick Eggenberger
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
Cristina Chiappini
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: georges.meynet@unige.ch
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Abstract

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We show that the peculiar surface abundance patterns of Carbon Enhanced Metal Poor (CEMP) stars has been inherited from material having been processed by H- and He-burning phases in a previous generation of stars (hereafter called the “Source Stars”). In this previous generation, some mixing must have occurred between the He- and the H-burning regions in order to explain the high observed abundances of nitrogen. In addition, it is necessary to postulate that a very small fraction of the carbon-oxygen core has been expelled (either by winds or by the supernova explosion). Therefore only the outermost layers should have been released by the Source Stars. Some of the CEMP stars may be He-rich if the matter from the Source Star is not too much diluted with the InterStellar Medium (ISM). Those stars formed from nearly pure ejecta would also be Li-poor.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2010

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