HR diagram for the sample when a) log g is based on Fe i-Fe ii ionisation equilibrium, and b) when log g is based on Hipparcos parallaxes. In b) the sizes of the circles are scaled with the difference between Fe i and Fe ii abundances. Red circles mark those stars where the Fe i abundances are lower than the Fe ii abundances, and vice versa for the blue circles. The α-enhanced Yonsei-Yale (Y2) isochrones by Demarque et al. (2004) have metallicities of [Fe/H]  =  −1 and + 0.3 dex, respectively, and are shown from 1 to 15 Gyr in steps of 1 Gyr.