3-DIMENSIONAL NUMERICAL-SIMULATION OF GASEOUS FLOW STRUCTURE IN SEMIDETACHED BINARIES

The results of numerical simulation of mass transfer in semidetached n on-magnetic binaries are presented. We, investigate the morphology of gaseous flows on the basis of three-dimensional gas-dynamical calculat ions of interacting binaries of different types (cataclysmic variables and low-mass X-ray binaries). We find that taking into account a circ umbinary envelope leads to significant changes in the stream-disc morp hology. In particular, the obtained steady-state self-consistent solut ions show an absence of impact between the gas stream from the inner L agrangian point L-1 and the forming accretion disc. The stream deviate s under the action of the gas of the circumbinary envelope, and does n ot cause the shock perturbation of the disc boundary (traditional hots pot). At the same time, the gas of the circumbinary envelope interacts with the stream and causes the formation of an extended shock wave, l ocated on the stream edge. We discuss the implication of this model wi thout hotspot (but with a shock wave located outside the disc) for int erpretation of the observations. The comparison of synthetic light cur ves with observations proves the validity of the discussed gas-dynamic al model without hotspot. We have also considered the influence of the circumbinary envelope on the mass transfer rate in semidetached binar ies. The obtained features of flow structure in the vicinity of L-1 sh ow that the gas of the circumbinary envelope plays an important role i n the flow dynamics, and that it leads to significant (in order of mag nitude) increase of the mass transfer rate. The most important contrib ution to this increase is from the stripping of the mass-losing star a tmosphere by interstellar gas flows, The parameters of the formed accr etion disc are also given in the paper. We discuss the details of the obtained gaseous flow structure for different boundary conditions on t he surface of mass-losing star, and show that the main features of thi s structure in semidetached binaries are the same for different cases. The comparison of gaseous flow structure obtained in two- and three-d imensional approaches is presented. We discuss the common features of the how structures and the possible reasons for revealed differences.