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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 ,
Raphael Hirschi ,
Sylvia Ekstrom ,
André Maeder ,
Cyril Georgy ,
Patrick Eggenberger  and
Cristina Chiappini
Georges Meynet
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: [email protected]
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: [email protected]
André Maeder
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: [email protected]
Cyril Georgy
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: [email protected]
Patrick Eggenberger
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: [email protected]
Cristina Chiappini
Affiliation:
Geneva Observatory, Geneva University, CH–1290 Sauverny, Switzerland email: [email protected]
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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.

Keywords

stars: AGBearly-typeevolution – supernovae: general – Galaxy: halo – nucleosynthesis
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S268: Light Elements in the Universe , November 2009 , pp. 141 - 146
Copyright
Copyright © International Astronomical Union 2010

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