Relativistic Radiative Winds from an Accretion Disk under Radiation Drag

Abstract

We examine the steady relativistic winds which are emanating from a luminous accretion disk and driven by disk radiation fields under the influence of radiation drag. For wind flows we use a streamline approach where the dynamical equations are expressed by the streamline coordinates, and a cold approximation where the pressure-gradient force is ignored. For radiation fields, on the other hand, we use a near-disk approximation where the radiation stress-energy tensors are evaluated from the disk region just below the flows. The streamlines may widen, since the wind flows gain angular momentum from the disk radiation field just below them. The wind terminal speed is smaller than the Icke's magic speed of (4-√7)c/3 ∼ 0.45c, because the streamlines are generally inclined, and therefore the radiative force is smaller than in the case of vertical streamlines. The conditions that the radiative wind blows are obtained for the control parameters: the radius of the wind base and the normalized disk luminosity. The radiative wind can blow from the inner region (r0 ∼ 5–8 rg) if the disk is sufficiently luminous. We also briefly discuss pure electron-positron pair winds, where the acceleration takes place very close to the disk.