Paβ luminosity as a function of L_acc,c. The black asterisks are the sample from Natta et al. (2004), the blue diamonds represent the sample analyzed by Muzerolle et al. (1998). The solid black line is the best-fitting relation found by Natta et al. (2004) (Eq. (2) of their paper). The green triangles are the objects of our sample, and the green line is the relation found combining these objects with the others.