Gaia CMD including the stars in the sample and other missing stars included in the ALS III catalog (Pantaleoni González et al., in prep.). All the stars have B_mag < 11 and distances below 4 kpc. The two diagonal dashed black lines mark the reddening line of a 20 M_⊙ star at the zero-age MS (ZAMS, bottom) and at 30 kK (top). Both are extended up to a Δ(A_V) = 2. Stars shown in green include those for which both the use of the maximum and minimum distances result in the star above the top reddening line. Those for which minimum distance locate them below the same reddening line are indicated in blue. Stars missing from the ALS III catalog are shown in gray. Four evolutionary tracks corresponding to 9, 15, 20, and 40 M_⊙ are included for reference. They were downloaded from the MESA Isochrones & Stellar Tracks online tool (MIST; see Dotter 2016; Choi et al. 2016; Paxton et al. 2013, 2015, for references purposes) for solar metallicity, no initial rotation, and A_V = 0.0. The average uncertainty in the y-axis is indicated in the legend, while it is negligible in the x-axis.