Radiative Disk Winds under Radiation Drag II

Abstract

Radiatively accelerated accretion-disk winds, which consist of ionized gas particles and are accelerated in disk radiation fields, were examined, taking into account radiation drag. For the present purpose, we quantitatively calculate the full components of radiation fields produced by a standard accretion disk around a black hole, considering the Doppler enhancement to the first order of v/c. As a result, there appear to be two major effects, which are dropped in the traditional radiative winds. First, a radiation-drag force appears, which is proportional to the particle velocity in this order and suppresses the motion of wind particles. Second, we emphasize that an azimuthal component of radiative flux appears, since the disk radiation field has angular momentum. % Using the components of radiation fields, we examined the radiative disk winds without imposing a near-disk approximation. Compared with the non-dragged winds, where the radiation-drag force is dropped, the acceleration in the vertical direction is suppressed due to the effect of radiation drag. That is, the radiation-drag force makes winds harder to blow than winds without the drag force. We obtained the escape condition of the radiative disk winds. In the present case, the disk wind blows from the inner disk when the disk luminosity exceeds 80% of the Eddington luminosity (in the case without the drag force it blows when the disk luminosity exceeds 60% of the Eddington luminosity). Moreover, these values become much smaller than the values obtained in a previous study, when the near-disk approximation was used, since the spatial variations of the disk radiation fields were fully taken into account in the present case.