A Study Of Physical Processes In The Contact Binary Systems

More than 50 percent stars are binaries. One special kind of binaries is called contact binaries, which arc characterized by the components filling the Roche lobes. Thus, the exchanges of mass and energy can journey to and fro between the components and a common envelope is formed. Many well known cataclysmic binaries are the products which are left over from the contact binaries, e.g., cataclysmic variables, novae, X-ray binaries, type-la supernovae.In the study of the structure and evolution of the contact binary, it is the most important to understand and analyze various complicated physical processes which have occurred in contact binaries. It is very significant for us to construct correct model and understand the evolutive properties of contact binaries. By analyzing these complicated physical processes and present models of contact binaries, we study a series of basic problems in this thesis. These problems which include the condition of contact binaries, the relationship of the exchanges of mass and energy and the conditions for starting and stopping of the mass exchange have been discussed in detail. Furthermore, the losses of mass and angular momentum via the outer Lagrange point, the effects of rotation and tide and the variations of theoretical light curves have been investigated and calculated carefully. They are the fundamental principles for studying and calculating various physical processes in contact binaries. The condition which the average effective potentials of the two components are greater than that of inner Lagrangian point is adopted as the condition of contact binaries. The mass flows in the common envelope of a contact binary, when the average potential of the primary differs from that of the secondary. This condition is defined as mass exchange. These conditions are stricter and more reasonable than the original ones, because the effects of rotation and tide are considered both in the calculations of the potential of the inner Lagrangian point and the average potentials at the surfaces of the components. In addition, the processes of mass transfer and the energy exchange are related to each other closely. When mass flows from one...