2004A&A...419..335N

Three-dimensional hydrodynamic calculations are performed in order to investigate mass transfer in a close binary system, in which one component undergoes mass loss through a wind. The mass ratio is assumed to be unity. The radius of the mass-losing star is taken to be about a quarter of the separation between the two stars. Calculations are performed for gases with a ratio of specific heats γ=1.01 and 5/3. Mass loss is assumed to be thermally driven so that the other parameter is the sound speed of the gas on the mass-losing star. Here, we focus our attention on two features: flow patterns and mass accretion ratio, which we define as the ratio of the mass accretion rate onto the companion, {dot}(M)_acc, to the mass loss rate from the mass-losing primary star, {dot}(M)_loss. We characterize the flow by the mean normal velocity of the wind on the critical Roche surface of the mass-losing star, V_R. When V_R<0.4AΩ, where A and Ω are the separation between the two stars and the angular orbital frequency of the binary, respectively, we obtain Roche-lobe over-flow (RLOF), while for V_R>0.7AΩ we observe wind accretion. We find very complex flow patterns in between these two extreme cases. We derive an empirical formula of the mass accretion ratio as 0.18x10^–0.75VR_/AΩ^ in the low velocity regime and 0.05(V_R/AΩ)^–4 in the high velocity regime.