Semi-major axis, in units of the initial orbital radius as a function of time in orbits for q = 0.001. The solid curve give the results from numerical simulation, and the curve with imposed crosses is obtained using Eq. (7) with contributions to the total torque for m ≤ 100 obtained from Eq. (22). However, the main contribution comes from m = 1 in this case (see Sect. 5.1 below). The numerical simulation was performed with no accretion onto the companion.