Bibcode
Allende Prieto, C.; Barklem, P. S.; Lambert, D. L.; Cunha, K.
Referencia bibliográfica
Astronomy and Astrophysics, v.420, p.183-205 (2004)
Fecha de publicación:
6
2004
Revista
Número de citas
334
Número de citas referidas
294
Descripción
We report the results of a high-resolution spectroscopic survey of all
the stars more luminous than M_V = 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 R ≃ 50 000, continuous spectral coverage
between ˜ 362-921 nm, and typical signal-to-noise ratios in the
range 150-600. 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.
Based on observations made with the 2.7 m telescope at the McDonald
Observatory of the University of Texas at Austin (Texas), and the 1.52 m
telescope at the European Southern Observatory (La Silla, Chile) under
the agreement with the CNPq/Observatorio Nacional (Brazil).
Tables 3-5 are only available in electronic form at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/420/183