Sample stars in the log T_eff − log g-plane. Black/red dots denote CN-unmixed/mixed chemical composition and open thick circles objects near/beyond core-H exhaustion. Wide circles surrounding the dots mark magnetic stars. Error bars denote 1σ-uncertainties. Data from double-lined detached eclipsing binary stars (Torres et al. 2010) are shown for comparison (small triangles). Overplotted are evolution tracks for non-rotating stars at Z = 0.014 from Ekström et al. (2012), for initial masses as indicated, and isochrones for log τ_evol(yr) = 6.5, 7.0, 7.5 and 8.0 (dotted lines, left to right). The position of the ZAMS is indicated by the long-dashed line. The sample stars are marked according to the numbering scheme introduced in Table 1.