Accretion-Disk Corona Advected by External Radiation Drag II. Relativistic Case

Abstract

We examined the accretion-disk corona (β-corona) for a relativistic case under the pseudo-Newtonian approximation. The β-corona is dynamically driven via radiation drag exerted by a central luminous source and an α accretion disk, itself. The corona is assumed to be geometrically thin and optically thin. When the central source is sufficiently luminous, the specific angular momentum of the corona gas is lost by radiation drag of the radiation field produced by the central source. As a result, the rotational velocity of the corona gas becomes smaller than the Keplerian one, and the corona gas is advected inward on a dynamical timescale — a dynamical disk corona. When the accretion disk is luminous, on the other hand, the corona gas tends to corotate with the underlying disk by radiation drag of the radiation field produced by the α -disk. As a result, the advection of the corona gas is suppressed. Emission-line profiles expected from such an advected disk corona were also calculated, particularly bearing in mind the recently observed X-ray line of MCG–6–30–15. The line profiles are generally double peaked where the blue peaks are stronger than the red peaks because of relativistic effects. The separation of the two peaks depends on the brightness of the central source as well as the size of the emitting regions. The best-fit parameters for MCG–6–30–15 are the followings: the central luminosity normalized by the Eddington luminosity 0.6, the normalized disk luminosity also 0.6, the central radius of the emitting region 5 Schwarzschild radii, the width of the emitting region also 5 Schwarzschild radii, and the inclination angle 30°.