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

TL;DR

This study investigates how radiation-drag effects influence line-force-driven winds from accretion disks in AGNs, revealing significant reductions in wind speed, mass outflow, and power, thereby refining models of UFOs.

Contribution

It introduces a non-hydrodynamic approach to quantify the impact of radiation-drag effects on line-force-driven winds from black hole accretion disks, highlighting their weakening influence.

Findings

Radiation-drag effects reduce wind maximum speed by 60-70%.

Mass outflow rates decrease by 50-80% with radiation-drag effects.

Kinetic power of winds drops by about an order of magnitude.

Abstract

Ultra-fast outflows (UFOs) with mildly relativistic velocities are measured using the X-ray spectra of radio-quiet and -loud active galactic nuclei (AGNs). In general, UFOs are believed to be generated from the accretion disk around a black hole (BH). A line-force driving model is suggested to be the mechanism to drive UFOs from the accretion disk. 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 disk. 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 $\sim$60\%--70\%, the mass outflow rate is reduced by $\sim$50\%--80\%, and the kinetic power is reduced by about an order of magnitude. The radiation-drag effects narrow the area where the winds are generated.