FGK Benchmark Stars A new metallicity scale

In the era of large spectroscopic surveys of stars of the Milky Way, atmospheric parameter pipelines require reference stars to evaluate and homogenize their values. We provide a new metallicity scale for the FGK benchmark stars based on their corresponding fundamental effective temperature and surface gravity. This was done by analyzing homogeneously with up to seven different methods a spectral library of benchmark stars. Although our direct aim was to provide a reference metallicity to be used by the Gaia-ESO Survey, the fundamental effective temperatures and surface gravities of benchmark stars of Heiter et al. 2013 and their metallicities obtained in this work can also be used as reference parameters for other ongoing surveys, such as Gaia, HERMES, RAVE, APOGEE and LAMOST.