Location of 121 of the stars in our sample in the Kiel (left) and spectroscopic HR (right) diagrams. Open symbols indicate stars for which we have detected clear or likely signatures of spectroscopic binarity. Triangles are stars for which only upper or lower limits in any of the two parameters used to construct these diagrams (T_eff and log g) could be obtained. Individual uncertainties are included as error bars. Evolutionary tracks and position of the ZAMS from the non-rotating, solar metallicity models by Ekström et al. (2012) and Georgy et al. (2013) are included for references. The dotted diagonal lines in the sHR diagram are the isocontours of constant gravity. We note that those seven early O-type stars flagged as Q4 (see Sect. 4.1) are not included in the figures.