Ratio of the complex parts of the Love number for the dynamical to equilibrium tide (Im(k₂²)_IGW/Im(k₂²)_eq) as a function of the orbital period and stellar age for a M_ZAMS = 1 M_⊙ star. The critical period, P_c, above which companions excite progressive IGWs, is shown in orange. R_⋆ (in brown) represents the orbital period on which a planet orbits at the surface of the star, and the Roche limit is given in purple. Changes in the stellar evolutionary phase are indicated with ticks on the upper axis.