Position of the L₁ point relative to the donor center of mass at the periapsis of the binary orbit in units of the instantaneous binary separation. The thick lines show the numerical solutions of Eq. (11). The dotted, dashed, and thin lines illustrate the high-q, low-f_don, and global-L₁ models, respectively. Blue, orange, and green correspond to f_don = 0.5, 1.0, and 1.5, respectively, and e = 0.3 for all models. The low-f_don prescription is independent of f_don.