Type I X-ray bursts and superbursts on neutron stars release sudden and intense radiation fields into their surroundings. Here, we consider the possible effects of these powerful explosions on the structure of the accretion disk. The goal is to account for the apparent evolution of the innermost regions of the accretion disk around 4U 1820–30 during a superburst. Three different processes are c...

The effect of an accretion disk on the Blandford-Znajek process and the evolution of a black hole are discussed using a simplified system for the black hole accretion disk in which the accretion rate is supposed to be dominated by the strong magnetic field on the disk. The evolutions of the mass and the angular momentum of the black hole are formulated and discussed with numerical calculations....

We consider supercritical accretion onto a compact object when the accretion rate exceeds its value derived from the Eddington limit: ṀEdd = LEdd/c . We use the scenario that was proposed by Shakura and Sunyaev (1973) for the supercritical regime, according to which matter flows out of the gas-disk surface under radiation pressure. An analytic solution of the accretion-disk structure is obtaine...

We propose a new model for the disk-jet connection in black hole x-ray transients and active galactic nuclei. In our model, the inner part of the accretion disk around the central black hole switches between two states. In one state, the accretion energy is dissipated locally (some within the disk, some within a corona) to produce the observed disk luminosity. In the second state, the accretion...

We study numerically the evolution of rotating cloud cores, from the collapse of a magnetically supercritical core to the formation of a protostar and the development of a protostellar disk during the main accretion phase. We find that the disk quickly becomes unstable to the development of a spiral structure similar to that observed recently in AB Aurigae. A continuous infall of matter from th...

Abstract. We calculate the structure of accretion disk around a spinning black hole for accretion rates Ṁ = 0.01− 10M⊙ s−1. The model is fully relativistic and treats accurately the disk microphysics including neutrino emissivity, opacity, electron degeneracy, and nuclear composition. We find that the accretion flow always regulates itself to a mildly degenerate state with the protonto-nucleon ...

A fraction of the radiation produced by an accretion disk may be Thomson scattered by a wind flowing away from the disk. Employing a simple plane-parallel model of the wind, we calculate the polarization of the scattered radiation and find that its sign depends on the wind velocity, β = v/c. In the case, 0.12 < β < 0.78, the polarization is parallel to the disk normal, i.e., it is orthogonal to...

We investigate a corona coupled with underlying disk through magnetic field and radiation field, and present emergent spectra. Due to buoyancy the magnetic flux loop emerges from the disk and reconnects with other loops in the corona, thereby releasing the magnetic energy to heat the coronal plasma. The energy is then radiated away through Compton scattering. By studying the energy balance in t...

We present a pseudo-Newtonian potential for accretion disk modeling around rotating black holes. This potential can describe the general relativistic effects in accretion disk properly. As the inclusion of rotation in a proper way is very important at the inner edge of the disk we derived our potential starting from the Kerr metric. This potential can reproduce all the essential properties of g...

We investigate various models of accretion disks for Sgr A*, one of the most puzzling sources in the Galaxy. The generic image we have taken into account consists of a black hole, an accretion disk, and a jet. Various accretion models are able to explain the low NIR ux of Sgr A*: a standard accretion disk with a jet, an ADAF, or an EDAF (Ejection Dominated Accretion Flow) model. We nd that all ...