Top panel: gravity (log g) dependence on the iron abundance ([Fe/H]) relative to the Sun for radial velocity members (filled) and non-members (unfilled). The typical individual measurement error is given in the upper left corner. Bottom panel: histogram of the iron abundance, including only the cluster dwarfs (log g >  4). The median value of the distribution (solid line) is [Fe/H]_cluster = −0.07 ± 0.1. The dashed lines show the standard deviation.