Formation of a contact binary star system

The process of forming a contact binary star system is investigated in the light of current knowledge of the W Ursae Majoris type eclipsing binaries and the current rotational braking theories for contracting stars. A preliminary stage of mass transfer is proposed and studied through the use of a computer program which calculates evolutionary model sequences. The detailed development of both stars is followed in these calculations, and findings regarding the internal structure of the star which is receiving the mass are presented. Relaxation of the mass-gaining star is also studied; for these stars of low mass and essentially zero age, the star eventually settles to a state very similar to a zero-age main sequence star of the new mass. A contact system was formed through these calculations; it exhibits the general properties of a W Ursae Majoris system. The initial masses selected for the calculation were 1.29 M/sub solar mass/ and 0.56 M/sub solar mass/. An initial mass transfer rate of about 10-10 solar masses per year gradually increased to about 10-8 solar masses per year. After about 2.5 x 107 years, the less massive star filled its Roche lobe and an initial contact system was obtained. The final masses were 1.01359 M/sub solar mass/ and 0.83641 M/sub solar mass/. The internal structure of the secondary component is considerably different from that of a main sequence star of the same mass