Prague Relativistic Astrophysics

Jan Cechura

The Roche lobe overflow and the isotropic radial stellar wind were traditionally considered as two competitive scenarios to explain the regime of mass loss from a companion star which can feed an accretion disc around a compact object in interacting binaries and X-ray binaries in particular. We have developed a radiation-hydrodynamic model of circumstellar matter and used it to numerically simulate the properties of the evaporative stellar wind from a supergiant component of a binary. Those simulations include radial approximation and also full 3D radiation-hydrodynamics taking into account the Roche potential, Coriolis force and radiative pressure in the continuum and lines. The Coriolis force influences substantially the mass-loss and thus also the accretion rate. Our results show that non-radial models are necessary to reach quantitative information about the angular modulation of the wind and the mass-loss and accretion rates with an accuracy of about tens of percents. Furthermore, the focusing of the stellar wind by the gravitational field of the compact companion leads to the formation of a gaseous tail behind the companion which can be understood as a modified version of the Bondi-Hoyle-Lyttleton accretion. Nowadays, the existence of such gaseous tails in interacting binaries is confirmed observationally.