Extra broadening rates (in km s^-1) for the O-star sample as a function of vsini (upper panel) and T_eff (lower panel). In both panels, luminosity class I stars are colored in dark blue, luminosity class II and III objects in light blue, and luminosity class IV and V objects in green. Intermediate (110 ≤ vsini (FT+GOF) ≤ 200 km s^-1) and fast rotating stars (vsini (FT+GOF) > 200 km s^-1) are additionally marked by large circles. In the upper panel, the solid line indicates the one-to-one relation.