Position of the program stars in the Kiel diagram. Evolutionary tracks for rotating (Ω/Ω_crit = 0.4) MS stars of solar metallicity and different initial masses (Georgy et al. 2013) are overlaid in red. Red filled circles and numbers mark the age in Myr. The locus of the zero-age MS (ZAMS) is indicated as a gray dashed line. Error bars are 1σ and cover statistical and systematic uncertainties. The two objects (B576, B598) for which a MS nature is unlikely are marked in gray (see Sect. 6.2.3).