Galactic and LMC O-dwarf results plotted in the T_eff–log g diagram (same symbols as Fig. 1). Evolutionary tracks (solid grey lines, with initial masses as indicated at the ZAMS) and isochrones (dotted purple lines) are from Brott et al. (2011) for solar metallicity; the ZAMS for both Z = Z_⊙ and 0.5 Z_⊙ are indicated as black lines. The blue region indicates where the O7 V stars are located.