Issue |
A&A
Volume 449, Number 1, April I 2006
|
|
---|---|---|
Page(s) | 127 - 134 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20053770 | |
Published online | 16 March 2006 |
Chemical abundances of 32 mildly metal-poor stars
1
Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China e-mail: zhw@bac.pku.edu.cn
2
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
Received:
22
July
2005
Accepted:
26
October
2005
Context.The formation scenario of the Galactic thick disk is an unresolved
problem. Chemical abundances in long-lived dwarf stars of the
thin and thick disks provide information of the Galactic disk
formation.Aims.We present photospheric abundances of the O, Na, Mg, Al, Si, Ca, Sc, Ti, V,
Cr, Mn, Ni, and Ba elements for 32 mildly metal-poor stars with .
According to their kinematics, age, and [ α/Fe] , sample stars are
identified to thin disk, thick disk, and halo population memberships. Element
abundances for sample stars are discussed as a function of
metallicity.Methods.High resolution and high signal-to-noise ratio spectra were obtained
with the Coudé Echelle Spectrograph mounted on the 2.16 m telescope at the National
Astronomical Observatories (Xinglong, China). Effective temperatures were estimated
from colour indices, and surface gravities from Hipparcos parallaxes. Stellar abundances
were determined from a differential LTE analysis. The kinematics parameters were calculated
from the parallax, proper motion, and radial velocity. Stellar ages were determined from
theoretical stellar evolution tracks.Results.The average age of the thick disk stars is older than the thin disk stars. Our element
abundance results extend and confirm previous works. The oxygen and other α-elements
(Mg, Si, Ca, and Ti) abundances of thin and thick disk stars show distinct trends at
. The [Al/Fe] behaviour is exactly as an α-element, although the
separation for [Na/Fe] of thin and thick disk stars is not clear. The elements V, Cr, and Ni
follow Fe very closely, and
there is no offset between thin and thick disk stars, but the Sc and Mn
abundance trends of the thin and thick disk stars are different,
and
[Ba/Fe] of thin disk and thick disk stars shows different behaviour.
© ESO, 2006
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