Critical angular momentum transfer to the binary as a function of the binary mass ratio for different values of the accretion factor; see Eq. (9). If the binary receives angular momentum at a rate higher than j_s, crit, then its orbit expands. We display five different values for the factor f that enclose all cases between the two limiting cases of f = 0 (accretion only on the primary) and f → ∞ (accretion only on the secondary).