Circulation and eccentricity plot. Top panel: circulation or libration period P_mod of the angle ŋ vs. the eccentricity e_c of the outer planet c in the BD+00 444 system. The modulation of the eccentricity e_b of the orbit of the inner planet occurs with the same period. Lower panel: the equilibrium eccentricity $e_{\text{p}}^{(\text{eq})}$ of the orbit of the inner planet BD+00 444 b (black line, left axis) and the average tidal power 〈P_tide〉 dissipated in its interior (red line, right axis) vs. the eccentricity of the orbit of the outer planet.