Top: sHR diagrams for the sample of O stars in Cygnus OB2 with reliable astrometry using Geneva (Ekström et al. 2012, considering non-rotating models on the top and rotating models on the bottom, respectively) evolutionary stellar tracks and isochrones. The sample is also subdivided into the stellar groups found by Berlanas et al. (2018b). Bottom: sHR diagrams for the sample of O stars in Cygnus OB2 that have not passed the criterion for reliable astrometry considering the same set of tracks and isochrones. The yellow triangle indicates an upper limit for log g.