Models for extremely metal-poor halo stars

Two alternative scenarios concerning the origin and evolution of extremely metal-poor halo stars are investigated. The first one assumes that the stars have been completely metal-free initially and produced observed carbon and nitrogen overabundances during the peculiar core helium flash typical of...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2004-07, Vol.422 (1), p.217-223
Main Authors: Weiss, A., Schlattl, H., Salaris, M., Cassisi, S.
Format: Article
Language:English
Subjects:
brown dwarfs
stars: abundances
stars: evolution
stars: individual: HE 0107–5240
stars: interiors
stars: low mass
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Summary:Two alternative scenarios concerning the origin and evolution of extremely metal-poor halo stars are investigated. The first one assumes that the stars have been completely metal-free initially and produced observed carbon and nitrogen overabundances during the peculiar core helium flash typical of low-mass Population III stars. The second scenario assumes that the initial composition resulted from a mixture of primordial material with ejecta from a single primordial supernova. Both scenarios are shown to have problems in reproducing C, N, and O abundances simultaneously, and both disagree with observed $^{12}{\rm C}/^{13}{\rm C}$-ratios, although in different directions. We concentrate on the most iron-poor, carbon-rich object of this class, HE 0107–5240, and conclude that the second scenario presently offers the more promising approach to understand these objects, in particular because evolutionary tracks match observations very well.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361:20040248