Left panel: evolution of the Rossby number for an isolated 1 M_⊙ stellar model during the PMS phase and the very early MS phase for different values of the initial rotation. The initial rotation periods and velocities can be seen in Fig. A.1. The Rossby number corresponding to the slowest initial rotation is the upper curve. Right panel: evolution of the X-ray, EUV luminosities and of their sum for a slow (in blue) and a fast (in red) rotating 1 M_⊙ model. The slow and fast rotations correspond, respectively, to the slowest and fastest model shown in Fig. A.1.