Hα flux versus T_eff for the γ Vel (left panel) and the Cha I (right panel) members observed with GIRAFFE and UVES. The symbol size scales with the vsini. The accretor candidates (10%W_Hα> 270 km s^-1) are denoted with filled symbols and typically have a larger flux than the other stars. The candidates that have been rejected on the basis of the EW_Hα criterion (Sect. 3.5) are marked with crosses. The flux values corrected for veiling by the factor (1 + r) are denoted by arrowheads. In each box, the dashed straight line is drawn to follow the upper envelope of the sources without accretion, while the dotted line is the saturation criterion adopted by Barrado y Navascués & Martín (2003) to separate classical from weak T Tauri.