Orbital decay timescale as a function of the pericentric distance q for a Jovian-mass planet in an initial quasi-parabolic orbit. Black curve is the prediction of the equilibrium tide model ( Q′ _p = 5 × 10 ⁶), while the red curve is the numerical estimate from the dynamical model from Ivanov & Papaloizou (2011). The dashed curve was obtained from the equilibrium tide model by modifying the tidal parameters according to Equation (5).