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Centro de Astrofísica da Universidade do Porto

Gaia FGK benchmark stars: Metallicity

P. Jofré, U. Heiter, C. Soubiran, S. Blanco-Cuaresma, C. Worley, E. Pancino, T. Cantat-Gaudin, L. Magrini, M. Bergemann, J. I. González Hernández, V. Hill, C. Lardo, P. de Laverny, K. Lind, T. Masseron, D. Montes, A. Mucciarelli, T. Nordlander, A. Recio-Blanco, J. Sobeck, R. Sordo, S. G. Sousa, H. M. Tabernero, A. Vallenari, S. Van Eck

Abstract
Context. To calibrate automatic pipelines that determine atmospheric parameters of stars, one needs a sample of stars, or “benchmark stars”, with well-defined parameters to be used as a reference.
Aims.
We provide detailed documentation of the iron abundance determination of the 34 FGK-type benchmark stars that are selected to be the pillars for calibration of the one billion Gaia stars. They cover a wide range of temperatures, surface gravities, and metallicities.
Methods.
Up to seven different methods were used to analyze an observed spectral library of high resolutions and high signal-to-noise ratios. The metallicity was determined by assuming a value of effective temperature and surface gravity obtained from fundamental relations; that is, these parameters were known a priori and independently from the spectra.
Results.
We present a set of metallicity values obtained in a homogeneous way for our sample of benchmark stars. In addition to this value, we provide detailed documentation of the associated uncertainties. Finally, we report a value of the metallicity of the cool giant ψ Phe for the first time.

Keywords
standards – techniques: spectroscopic – surveys – stars: fundamental parameters

Astronomy and Astrophysics
Volume 564, Page A133_1
April 2014

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