Gaia FGK benchmark stars: Metallicity
Montes, D.; de Laverny, P.; Cantat-Gaudin, T.; Lardo, C.; Vallenari, A.; Soubiran, C.; Heiter, U.; Sordo, R.; Pancino, E.; Blanco-Cuaresma, S.; Sousa, S. G.; Tabernero, H.; González Hernández, J. I.; Mucciarelli, A.; Jofré, P.; Lind, K.; Masseron, T.; Sobeck, J.; Nordlander, T.; Hill, V.; Magrini, L.; Van Eck, S.; Worley, C. C.; Bergemann, M.; Recio Blanco, A.
United Kingdom, France, Sweden, Italy, Germany, Spain, Belgium, United States, Portugal
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