Issue |
A&A
Volume 420, Number 1, June II 2004
|
|
---|---|---|
Page(s) | 183 - 205 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20035801 | |
Published online | 14 May 2004 |
S
N: A spectroscopic survey of stars in the solar neighborhood *,**
The Nearest 15 pc
1
McDonald Observatory and Department of Astronomy, University of Texas, Austin, TX 78712-1083, USA e-mail: dll@astro.as.utexas.edu
2
Uppsala Astronomical Observatory, Box 515, 751-20 Uppsala, Sweden e-mail: barklem@astro.uu.se
3
Observatório Nacional, Rua General José Cristino 77 CEP 20921-400, Rio de Janeiro, Brazil e-mail: katia@on.br
Corresponding author: C. Allende Prieto, callende@astro.as.utexas.edu
Received:
4
December
2003
Accepted:
3
March
2004
We report the results of
a high-resolution spectroscopic survey of all the stars more
luminous than MV = 6.5 mag within 14.5 pc from the Sun.
The Hipparcos
catalog's completeness limits guarantee that our survey is comprehensive and
free from some of the selection effects in other samples of nearby
stars.
The resulting spectroscopic database, which we have made publicly available,
includes spectra for 118 stars obtained with
a resolving power of , continuous spectral coverage
between
nm, and typical signal-to-noise ratios in the range
. We derive
stellar parameters and perform
a preliminary abundance and kinematic analysis of the F-G-K stars
in the sample. The inferred metallicity ([Fe/H]) distribution is centered
at about -0.1 dex, and shows a standard deviation of 0.2 dex.
A comparison with larger samples of Hipparcos stars, some of which
have been part of previous abundance studies, suggests that our
limited sample is representative of a larger volume of the local thin disk.
We identify a number of metal-rich K-type stars which appear to be very old,
confirming the claims for the existence of such stars in the solar
neighborhood.
With atmospheric effective temperatures and gravities
derived independently of the spectra, we find that our classical LTE
model-atmosphere analysis of metal-rich (and mainly K-type) stars
provides discrepant abundances from neutral and ionized lines of
several metals.
This ionization imbalance could be a sign of departures from LTE
or inhomogeneous structure, which are ignored in the interpretation of the
spectra. Alternatively, but seemingly unlikely,
the mismatch could be explained by systematic errors
in the scale of effective temperatures.
Based on transitions of majority species, we discuss abundances of 16
chemical elements. In agreement with earlier studies
we find that the abundance ratios to iron
of Si, Sc, Ti, Co, and Zn become smaller as the iron abundance increases
until approaching the solar values, but the trends reverse for higher
iron abundances.
At any given metallicity,
stars with a low galactic rotational velocity
tend to have high
abundances of Mg, Si, Ca, Sc, Ti, Co, Zn, and Eu, but low
abundances of Ba, Ce, and Nd.
The Sun appears deficient by roughly 0.1 dex
in O, Si, Ca, Sc, Ti, Y, Ce,
Nd, and Eu, compared to its immediate neighbors
with similar iron abundances.
Key words: surveys / stars: fundamental parameters / stars: abundances / Galaxy: solar neighbourhood
© ESO, 2004
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