Relation between energy transfer and evolution of W UMa-type binaries

In the present article the relation between the energy transfer rate from the primary to the secondary and the evolutionary degree of W UMa-type binaries is given and the energy transfer rates and the evolution degrees of three W UMa-type contact binaries (TV Mus, SS Ari and RZ Com) are calculated. The analyzed results show that the maximum value of the energy transfer rate is basically determined by the mass ratio. The greater the mass ratio, the greater the maximum possible value of the energy transfer rate. The energy transfer rate is related to the evolutionary degree of the primary, and the greater the evolutionary degree of the primary, the smaller the energy transfer rate. The energy transfer from the primary to the secondary could stop when the evolutionary degree of the primary reaches a specific value which is determined by a property of the system.