Effect of radiation drag on the line-force-driven winds

Abstract

ABSTRACT Ultra-fast outflows (UFOs) with mildly relativistic velocities are measured using the X-ray spectra of radio-quiet and -loud active galactic nuclei. In general, UFOs are believed to be generated from the accretion disc around a black hole. A line-force driving model is suggested to be the mechanism to drive UFOs from the accretion disc. In this paper, we use the non-hydrodynamic approach to examine the influences of radiation-drag effects on the line-force-driven winds generated from the accretion disc. We find that the radiation-drag effects can significantly weaken the line-force-driven winds. Compared with the case without the radiation-drag effects, when the radiation-drag effects are considered, the maximum speed of winds is reduced by ∼60 per cent–70 per cent, the mass outflow rate is reduced by ∼50 per cent–80 per cent, and the kinetic power is reduced by about an order of magnitude. The radiation-drag effects narrow the area where the winds are generated.