Abundance correlations in mildly metal-poor stars. II. Light elements (C to Ca)
Abstract
Accurate relative abundances have been obtained for carbon, oxygen, sodium, aluminium, silicon, and calcium in a sample of mildly metal-poor stars. This analysis complements a previous study carried out by Jehin et al. ([CITE], A&A, 341, 241), which provided the basis for the EASE scenario. This scenario postulates that field metal-poor stars were born in self-enriched proto-globular cluster clouds. By further investigating the correlations between the different α-element abundances, we propose a modified scenario for the formation of intermediate metallicity stars, in which the stars exhibiting lower than average α/Fe abundance ratios would form in low mass clouds, unable to sustain the formation of very massive stars (M ⪆ 30~M_⊙). Moreover, the carbon-to-iron ratio is found to decrease as one climbs the so-called Population IIb branch, i.e. when the s-element abundance increases. In the framework of the EASE scenario, we interpret this anticorrelation between the carbon and the s-element abundances as a signature of a hot bottom burning process in the metal-poor AGB stars which expelled the matter subsequently accreted by our Population IIb stars.
Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO Programmes 56.E-0384, 57.E-0400 and 59.E-0257).- Publication:
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Astronomy and Astrophysics
- Pub Date:
- April 2005
- DOI:
- 10.1051/0004-6361:20040507
- Bibcode:
- 2005A&A...433..285D
- Keywords:
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- stars: abundances;
- stars: Population II;
- stars: atmospheres;
- nuclear reactions;
- nucleosynthesis;
- abundances;
- Galaxy: evolution