Using idealized models of the accretion disk we investigate the relativistic effects on the energy deposition rate via neutrino pair annihilation near the rotation axis of a Kerr black hole. Neutrinos are emitted from the accretion disk. The bending of neutrino trajectories and the redshift due to the disk rotation and gravitation are taken into consideration. The Kerr parameter, a, affects not...

Within the standard accretion disk theory for active galactic nuclei (AGN), the observed X-rays are often modeled by Compton up-scattering of ultraviolet (UV) disk photons inside a hot disk corona. Here, we point out that for many AGN, radiation pressure due to the very same UV disk photons can drive a flow from the disk into the corona and couple the processes producing X-rays and UV photons. ...

We show that most of hot, optically thin accretion disk models which ignore advective cooling are not self-consistent. We have found new types of optically thin disk solutions where cooling is dominated by radial advection of heat. These new solutions are thermally and viscously stable. Subject headings: accretion, accretion disks | instabilities

This paper considers the gas phase chemistry in a protoplanetary accretion disk, especially the chemistry initiated in the gas phase by destruction of dust close to the central star. Slow radial particle transport moves gas and dust from the cold outer parts of a protoplanetary accretion disk into its warm central part where chemical reactions in the gas phase are activated. At the same time ga...

The analytical investigation of time-dependent accretion in disks is carried out. We consider a time-dependent disk in a binary system at outburst which has a fixed tidally-truncated outer radius. The standard model (Shakura-Sunyaev) of the disk is considered. The vertical structure of the disk is accurately described in two regimes of opacity: Thomson and free-free. The fully analytical soluti...

NGC 1068 is one of the best studied Seyfert II galaxies, for which the blackhole mass has been determined from the Doppler velocities of water maser. We show that the standard α-disk model of NGC 1068 gives disk mass between the radii of 0.65 pc and 1.1 pc (the region from which water maser emission is detected) to be about 7x10 M⊙ (for α = 0.1), more than four times the blackhole mass, and a T...

We present numerical magnetohydrodynamic (MHD) simulations of a magnetized accretion disk launching trans-Alfvénic jets. These simulations, performed in a 2.5 dimensional time-dependent polytropic resistive MHD framework , model a resistive accretion disk threaded by an initial vertical magnetic field. The resistivity is only important inside the disk, and is prescribed as η = α m V A H exp(−2Z...

Current stellar evolution models predict that during the core collapse of massive stars, a considerable amount of the stellar material will fall back onto the compact, collapsed remnants (neutron stars or black holes), usually in the form of an accretion disk. This triggers rapid mass accretion onto, e.g., the black hole, and produces energetic explosions known as Gamma-ray bursts. However it i...

We have analyzed the archival XMM-Newton data of the bright UltraLuminous X-ray Source (ULX) M82 X-1 with an 105 ksec exposure when the source was in the steady state. Thanks to the high photon statistics from the large effective area and long exposure, we were able to discriminate different X-ray continuum spectral models. Neither the standard accretion disk model (where the radial dependency ...

Using the black hole transient X-ray source A0620-00 as an example we study the physical interplay of three theoretical constituents for modelling these transient sources: (1) the advection-dominated accretion flow (ADAF) onto the central black hole, (2) the evaporation of matter from the cool outer disk forming a coronal flow and (3) standard disk evolution leading to outburst cycles by accret...