Radiative Disk Winds under Radiation Drag

Abstract

We consider accretion-disk winds, which are driven by disk radiation fields, while taking into account radiation drag as well as radiation pressure. The winds ejected from the accretion disk are exerted by the influence of the radiation pressure from the central object and the accretion disk, itself. We calculate, under the near-disk approximation, the trajectories of particles for various parameters, such as the initial radii and the luminosities of the central object and the disk. We then obtain the conditions which determine whether particles escape or not. These particles moving in intense radiation fields with a velocity of the order of the light speed are also affected by radiation drag. Due to the radiation-drag effect, dragged particle winds are hard to escape compared with the case of non-dragged winds. When they are captured by the gravitational force of the central object, particles float at some typical height above the accretion disk while being balanced by the vertical gravitational force of the central object and the force of the disk radiation pressure. In such a case, the ejected material becomes coronal gas spreading above/below the disk. When the winds blow, on the other hand, the trajectories of the particles tend to widen in the radial direction, since the winds are dragged by the disk radiation fields and gain angular momentum.