ΔΩ_phot vs. the effective temperature T_eff. The black bullets indicate the values measured in the present work. The filled bullets show stars that have reached the ZAMS, and the empty bullets show stars that are still contracting. The black crosses indicate the data reported in Barnes et al. (2005). The continuous and the dotted line depict the power law inferred in the present work and that inferred in Barnes et al. (2005). The dashed line indicates the power law predicted by the theoretical model of Küker & Rüdiger (2011). The T_eff values have been inferred from the models of Siess et al. (2000). The shaded area represents the uncertainty in our power-law fitting. The large gray bullets and the gray line represent the results of Reinhold et al. (2013).