Issue |
A&A
Volume 403, Number 3, June I 2003
|
|
---|---|---|
Page(s) | 1105 - 1114 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20030438 | |
Published online | 23 May 2003 |
First Stars. III. A detailed elemental abundance study of four extremely metal-poor giant stars *,**
1
Observatoire de Paris-Meudon, GEPI, 92195 Meudon Cedex, France
2
GRAAL, Université de Montpellier II, 34095 Montpellier Cedex 05, France
3
Department of Physics & Astronomy, Michigan State University, East Lansing, MI 48824, USA
4
IAG, Universidade de São Paulo, Departamento de Astronomia, CP 3386, 01060-970 São Paulo, Brazil
5
Astronomical Observatory, NBIfAFG, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
6
Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy
7
Lund Observatory, Box 43, 221 00 Lund, Sweden
8
European Southern Observatory (ESO), Karl-Schwarschild-Str. 2, 85749 Garching b. München, Germany
Corresponding author: P. François, Patrick.Francois@obspm.fr
Received:
27
December
2002
Accepted:
21
March
2003
This paper reports detailed abundance analyses for four extremely metal-poor (XMP)
giant stars with , based on high-resolution, high-
spectra from
the ESO VLT (Kueyen/UVES) and LTE model atmosphere calculations.
The derived
[ α/Fe] ratios in our sample exhibit a small dispersion, confirming previous
findings in the literature, i.e. a constant overabundance of the
α-elements with a very small (if any) dependence on [Fe/H]. In
particular, the very small scatter we determine for [Si/Fe] suggests that this element
shows a constant overabundance at very low metallicity, a conclusion which could
not have been derived from the widely scattered [Si/Fe] values reported in the literature
for less metal-poor stars. For the iron-peak elements, our precise
abundances for the four XMP stars in our sample confirm the decreasing trend of Cr and Mn with
decreasing [Fe/H], as well as the increasing trend for Co and the absence of any
trend for Sc and Ni. In contrast to the significant spread of the ratios [Sr/Fe]
and [Ba/Fe], we find [Sr/Ba] in our sample to be roughly solar, with a much lower
dispersion than previously found for stars in the range
.
Key words: stars: abundances / stars: Population II / Galaxy: abundances / Galaxy: halo / nuclear reactions, nucleosynthesis, abundances
© ESO, 2003
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