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Carbon-enhanced metal-poor stars as probes of early Galactic nucleosynthesis

Published online by Cambridge University Press:  09 March 2010

O. R. Pols ,
R. G. Izzard ,
E. Glebbeek  and
R. J. Stancliffe
O. R. Pols
Affiliation:
Sterrekundig Instituut Utrecht, P.O. Box 80000, NL-3584 TA Utrecht, The Netherlands email: [email protected]
R. G. Izzard
Affiliation:
Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP226, Boulevard du triomphe, B-1050 Bruxelles, Belgium
E. Glebbeek
Affiliation:
Dept. of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1, Canda
R. J. Stancliffe
Affiliation:
School of Mathematical Sciences, Monash University, P.O. Box 28M, Victoria 3800, Australia
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A large fraction, between 10 and 25%, of very metal-poor stars in the Galactic halo are carbon-rich objects, with enhancements of carbon relative to iron exceeding a factor 10. The majority of these carbon-enhanced metal-poor (CEMP) stars show enhancements of heavy s-process elements and have been found to be spectroscopic binary systems. Many of their properties are well explained by the binary mass transfer scenario, in which a former asymptotic giant branch (AGB) companion star has polluted the low-mass star with its nucleosynthesis products. The same scenario predicts the existence of nitrogen-rich metal-poor (NEMP) stars, with [N/C] > 0.5, from AGB companions more massive than about 3 solar masses. In contrast to CEMP stars, however, such NEMP stars are very rare. Recent studies suggest that the high frequency of CEMP stars requires a modified initial mass function (IMF) in the early Galaxy, weighted towards intermediate-mass stars. Such models also implicitly predict a large number of NEMP stars which is not seen.

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S265: Chemical Abundances in the Universe: Connecting First Stars to Planets , August 2009 , pp. 117
Copyright
Copyright © International Astronomical Union 2010

References

Izzard, R. G., Glebbeek, E., Stancliffe, R. J., & Pols, O. R. 2010, A&A in press (arXiv:0910.2158)Google Scholar