The sample stars with Strömgren photometric data in the T_eff–log g plane. Solutions from the spectroscopic determination are shown as dots, open circles mark values that are obtained using photometric indicators according to our calibrations using  [c₁]  and β. The two corresponding solutions are interconnected. Typical error bars are indicated in the upper left. Dotted lines mark evolution tracks for rotating stars at metallicity Z = 0.014 (Ekström et al. 2012), from 9 M_⊙ to 32 M_⊙ (bottom to top). The 9 M_⊙ model shows a blue loop, partially displayed here.