Fitted activity model to the PV data excluding HD 51062. This model has been subtracted in Fig. 3. The color code and white solid lines with contour levels show the more complex model (b) of Eq. (6). As expected, the most important parameter is age. The increase of significant activity timescales with age can also be seen: 99% of the final activity is reached after ∼5 d for a 10 Myr-old star, but only after ∼30 yr for a 10 Gyr-old star. The black dashed lines show the simpler model (a) of Eq. (5) where the timescales are forced to be the same for all ages.