GASDYNAMICAL TREATMENT OF MASS-TRANSFER IN SYMBIOTIC STARS

:The results of two-dimensional, non-adiabatic gas dynamical simulatio ns of gas flows in symbiotic stars are presented. It. is shown that fo r a binary system with components that do not fill their Roche lobes, the structure of the gaseous stream is determined not only by the flow from the vicinity of the inner Lagrangian point, but also by the flow of matter caused by the orbital motion of the accretor through the ga s of the stellar wind. The calculated gaseous flow structure consists of a set of shocks and tangential discontinuities. It is found that fo r all considered cases two bow shocks exist. One of the bow shocks is located in front of the accretor in the path of its orbital motion, an d the second one is between the components. It is found that matter is accreted in a spiral fashion, forming an accretion disk. In steady-st ate simulations, a structure with shocks (both trailing and leading) i n the disk was observed. Gas dynamical perturbations of the disk's out er edge by the accreting gas inflow lead to the formation of two inten sive trailing shocks propagating inward. Gas dynamical perturbations o f the inner part of the disk result in the occurrence of leading shock s. One possible mechanism for the generation of spiral shocks is dissi pative instability. The existence of spiral shocks results in a redist ribution of the angular momentum of the disk material and an increase of the accretion rate.