Characteristic periods as a function of the age of the system for stellar masses between 0.4 and 1.4 M_⊙. In dark gray we plot the region corresponding to tidal frequencies greater than N_max, for which no propagation of gravity waves is allowed. The colored areas correspond to orbital periods that are likely to excite progressive waves (with frequencies ω < ω_c) for each stellar mass. In purple we show typical values corresponding to the Roche limit. The dashed black line corresponds to an orbital period of one day.