Issue |
A&A
Volume 433, Number 1, April I 2005
|
|
---|---|---|
Page(s) | 285 - 295 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20040507 | |
Published online | 14 March 2005 |
Abundance correlations in mildly metal-poor stars*
II. Light elements (C to Ca)
1
Institute of Astrophysics and Geophysics, University of Liège, 17 Allée du 6 Août, 4000 Liège, Belgium e-mail: decauwer@astro.ulg.ac.be
2
European Southern Observatory, Casilla 19001, Alonso de Cordova 3107, Vitacura, Santiago, Chile
3
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Received:
23
March
2004
Accepted:
16
November
2004
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 ().
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.
Key words: stars: abundances / stars: Population II / stars: atmospheres / nuclear reactions, nucleosynthesis, abundances / Galaxy: evolution
© ESO, 2005
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