Hydrodynamics of Young Binaries with Low-Mass Secondaries

The model of a young star with a low-mass secondary component (q = M₂/M₁ <= 0.1) accreting matter from a circumbinary (CB) disc is considered. It is assumed that the orbit and the CB disc can be coplanar and non-coplanar. The model parameters were varied within the following ranges: the component mass ratioq ranged from 0.1 to 0.003, the eccentricity e varied from 0 to 0.7, the inclination of the orbit plane to the CB disc ranged from 0 to 10 degrees, and the parameter that defines the viscosity of the system was also varied. A number of hydrodynamics models of such a system have been calculated by the SPH method and then the variations of the circumstellar extinction and phase brightness curves were determined. The calculated brightness curves differ in shape and amplitude and it depends on the model parameters and the orientation of the system relative to the observer. The results were used to analyze the cyclic activity of UX Ori type stars.