“…We also investigated the merger of W UMa systems with an extreme mass ratio and well-determined physical parameters recently, it is found that a large amount of mass and angular momentum should be lost from binary systems, otherwise, the rotation velocities of merged single stars would exceed their breakup velocities [6]. The time dependence of contact degree F, effective temperature T eff of the primary (solid) and the secondary (dashed), together with the ratio of spin angular momentum to orbital angular momentum J rot /J orb , the luminosity transfer rate ∆L, the total mass, M tenv , contained in convective envelopes, and rate of AML [8]. The time dependence of contact degree F, effective temperature T eff of the primary (solid) and the secondary (dashed), together with the ratio of spin angular momentum to orbital angular momentum J rot /J orb , the luminosity transfer rate ∆L, the total mass, M tenv , contained in convective envelopes, and rate of AML [8].…”