Line Spectrum from Advection-Dominated Accretion Disks

Abstract

The emission-line profiles from advection-dominated accretion disks were calculated for a wide variety of parameters. As a model of advection-dominated disks, we adopted a self-similar solution by Narayan and Yi (1994, AAA 61.064.083) and a beta disk driven by radiation drag by Fukue and Umemura (1995, AAA 64.064.034). The emissivity assumed was a power of the radius. The parameters are then the size of the emitting regions, the power index of the emissivity, and the inclination angle, except for a few parameters inherent in each model. The line profiles in advection-dominated cases, like those from a Keplerian disk, are generally double peaked, partly due to the rotational motion and partly due to the radial infall motion. In a Keplerian disk and a self-similar disk the separation of peaks depends on the size of the emitting regions, whereas does not depend on the size so much in the beta disk. One of the strategies to distinguish these models is to observe the separation for the different species, which originate in different regions on the disk. In addition, the separation for advection-dominated accretion disks is systematically small, since the rotational velocity is generally smaller than the Keplerian velocity. In profile variations during an eclipse a blue peak disappears at first and a red peak follows in the Keplarian disks, while both peaks change simultaneously in avection-dominated accretion disks. This can be another strategy to discriminate models.

Evolution of a Luminous Hoyle-Lyttleton Accretor

“…If the black hole is non-luminous and the relative speed between the black hole and the GMC is sufficiently small (less than a few km s _1 ), the black hole terminates in the GMC with a timescale of 10 6 yr -syndrome. Subsequently, it consumes the GMC and eventually becomes a massive black hole (Fukue 1994).…”