Quadratic coefficients (Eq. (2)) that determine the curvature of the Roche potential near the Lagrangian point along the binary axis (A, left) and in the plane normal to the binary axis (B and C, right). The three coefficients are related by B = −(A + 3)/2 and C = B + 1. The red (blue) line represents the coefficients for the inner (outer) Lagrangian point, as a function of the donor mass over the accretor mass. In both panels, a few examples of mass transferring systems are presented in three different mass ratio regimes such as stellar extreme mass ratio inspiral (EMRI), even though the boundaries among these regimes are not clearly defined.