Index β_t vs. Hα wings index α_w, for UVES-POP stars (colored symbols). Datapoints from the γ Vel dataset are shown in gray (excluding stars of types later than about K7). γ Vel cluster members are indicated by gray crosses, and cluster CTTS in particular by empty gray circles. As explained in the legend, filled colored dots are UVES-POP stars of luminosity classes IV-V (or undefined), smaller empty circles are of class III (including intermediate classes such as II/III, or III/IV), and bigger empty circles are of luminosity classes I-II. Spectral classes are color-coded, as in the legend. Wolf-Rayet stars, OC/ON stars, subdwarfs, and carbon stars are plotted with black symbols. These and stars with peculiar spectra are labeled.