Illustration of a binary system configuration with non-synchronised rotations. The system is composed of 1 M_⊙ MS primary star and a 0.2 M_⊙ MS companion separated by r = 2R₁. The two grey planes are the planes of symmetry, each rotation axis is marked with a black line. The orbital rotation is originating from the system centre of mass, located inside the primary. The black curve is the secondary orbital path, a black axis is joining the centre of each star with and emphasis on the Lagrangian point L1. Finally, the colour code corresponds to the surface effective gravity, the local flux emitted by a star being a function of this quantity.