Bibcode
Ghezzi, L.; Dutra-Ferreira, Letícia; Lorenzo-Oliveira, Diego; Porto de Mello, Gustavo F.; Santiago, Basílio X.; De Lee, Nathan; Lee, Brian L.; da Costa, Luiz N.; Maia, Marcio A. G.; Ogando, Ricardo L. C.; Wisniewski, John P.; González Hernández, J. I.; Stassun, Keivan G.; Fleming, Scott W.; Schneider, Donald P.; Mahadevan, Suvrath; Cargile, Phillip; Ge, Jian; Pepper, Joshua; Wang, Ji; Paegert, Martin
Bibliographical reference
The Astronomical Journal, Volume 148, Issue 6, article id. 105, 21 pp. (2014).
Advertised on:
12
2014
Citations
12
Refereed citations
9
Description
Studies of Galactic chemical, and dynamical evolution in the solar
neighborhood depend on the availability of precise atmospheric
parameters (effective temperature T eff, metallicity [Fe/H],
and surface gravity log g) for solar-type stars. Many large-scale
spectroscopic surveys operate at low to moderate spectral resolution for
efficiency in observing large samples, which makes the stellar
characterization difficult due to the high degree of blending of
spectral features. Therefore, most surveys employ spectral synthesis,
which is a powerful technique, but relies heavily on the completeness
and accuracy of atomic line databases and can yield possibly correlated
atmospheric parameters. In this work, we use an alternative method based
on spectral indices to determine the atmospheric parameters of a sample
of nearby FGK dwarfs and subgiants observed by the MARVELS survey at
moderate resolving power (R ~ 12,000). To avoid a time-consuming manual
analysis, we have developed three codes to automatically normalize the
observed spectra, measure the equivalent widths of the indices, and,
through a comparison of those with values calculated with predetermined
calibrations, estimate the atmospheric parameters of the stars. The
calibrations were derived using a sample of 309 stars with precise
stellar parameters obtained from the analysis of high-resolution FEROS
spectra, permitting the low-resolution equivalent widths to be directly
related to the stellar parameters. A validation test of the method was
conducted with a sample of 30 MARVELS targets that also have reliable
atmospheric parameters derived from the high-resolution spectra and
spectroscopic analysis based on the excitation and ionization equilibria
method. Our approach was able to recover the parameters within 80 K for
T eff, 0.05 dex for [Fe/H], and 0.15 dex for log g, values
that are lower than or equal to the typical external uncertainties found
between different high-resolution analyses. An additional test was
performed with a subsample of 138 stars from the ELODIE stellar library,
and the literature atmospheric parameters were recovered within 125 K
for T eff, 0.10 dex for [Fe/H], and 0.29 dex for log g. These
precisions are consistent with or better than those provided by the
pipelines of surveys operating with similar resolutions. These results
show that the spectral indices are a competitive tool to characterize
stars with intermediate resolution spectra.
Based on observations obtained with the 2.2 m MPG telescope at the
European Southern Observatory (La Silla, Chile), under the agreement
ESO-Observatório Nacional/MCT, and the Sloan Digital Sky Survey,
which is owned and operated by the Astrophysical Research Consortium.
Related projects
Very Low Mass Stars, Brown Dwarfs and Planets
Our goal is to study the processes that lead to the formation of low mass stars, brown dwarfs and planets and to characterize the physical properties of these objects in various evolutionary stages. Low mass stars and brown dwarfs are likely the most numerous type of objects in our Galaxy but due to their low intrinsic luminosity they are not so
Rafael
Rebolo López