THE OUTFLOWING REGIME OF QUASI-SPHERICAL ACCRETION ON TO X-RAY COMPACT OBJECTS

We study numerically the quasi-spherical accretion of matter on to a relativistic object with anisotropic X-ray luminosity which is powered by mass accretion. The X-rays heat the accreting gas through Compton scattering. When the gas temperature increases above the local escape temperature, part of the accreting gas will flow outwards as a result of the action of buoyancy force. The direction of the outflow coincides with the maximum of the X-ray luminosity. The depth of outflow as well as the velocity of the stream is correlated with the energy of X-ray quanta. The outflow exists persistently, but the mass-loss rate in the outflow is highly variable (approximately 50 per cent). In spite of its quantum nature, Compton heating markedly affects the gas, forcing the matter outflow at X-rav luminosities as small as three orders of magnitude less than the Eddington limit. The phenomenon of hot gas outflow takes place in the case of accretion on to a wind-fed X-ray source (neutron star or black hole) in a wide binary and in the case of a supermassive black hole in an active galactic nucleus (QSO or Seyfert).