Related papers: Light rays and wave fronts in strong gravity
The evolution of an accretion disk, formed as a consequence of the disruption of a star by a black hole, is followed by solving numerically the hydrodynamic equations. The present investigation aims to study the dependence of resulting…
Hot spots residing on the surface of an accretion disc have been considered as a model of short-term variability of active galactic nuclei. In this paper we apply the theory of random point processes to model the observed signal from an…
Recently, the issue of the role of the Eddington limit in accretion discs became a matter of debate. While the classical (spherical) Eddington limit is certainly an over-simplification, it is not really clear how to treat it in a flattened…
We study the optical paths of the light rays propagating inside a nonlinear moving dielectric media. For the rapidly moving dielectrics we show the existence of a distinguished surface which resembles, as far as the light propagation is…
Disc spectra from highly luminous black hole binaries are observed to be rather simple, despite theoretical predictions to the contrary. We collate the disc-dominated spectra from multiple observations of 10 separate sources, and show that…
It is commonly believed that accretion discs are truncated and their inner regions are described by advection dominated accretion flows (ADAFs) in the hard spectral state of black hole X-ray binaries. However, the increasing occurrence of a…
Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes in the accretion flow lead to stochastic variability of this emission on a wide…
The galactic black hole binary systems give an observational template showing how the accretion flow changes as a function of increasing mass accretion rate, or L/L_Edd. These data can be synthetised with theoretical models of the accretion…
We consider thin accretion disks in the field of a class of rotating regular black holes. For this purpose, we obtain the radius of the innermost stable circular orbit, $r_{ISCO}$ and efficiency of accretion disk in converting matter into…
The centers of elliptical galaxies host supermassive black holes that significantly affect the surrounding interstellar medium through feedback resulting from the accretion process. The evolution of this gas and of the nuclear emission…
Accreting black holes often show iron line emission in their X-ray spectra. When this line emission is very broad or variable then it is likely to originate from close to the black hole. The theory and observations of such broad and…
It is commonly assumed that in black hole accretion disks the angular momenta of the disk and the black hole are aligned. However, for a significant fraction of stellar mass black holes and supermassive black holes, the momenta may not be…
Luminous accreting stellar mass and supermassive black holes produce power-law continuum X-ray emission from a compact central corona. Reverberation time lags occur due to light travel time-delays between changes in the direct coronal…
Disk accretion may be the fundamental astrophysical process. Stars and planets form through the accretion of gas in a disk. Black holes and galaxies co-evolve through efficient disk accretion onto the central supermassive black hole.…
Two-dimensional accretion flows near black holes have been investigated by time-dependent hydrodynamical calculations. We assume that the flow is axisymmetric and that radiative losses of internal energy are negligible, so that the disc is…
In this paper,We present a simple relativistic approach to analyze the flux striking the disk which is possibly from a source up the Black hole.The X-ray source is locate above an accretion disc orbiting around the black hole,this…
Black holes are the most compact objects in the universe. Therefore, matter accreting onto is likely to radiate photons of energy comparable to very high gravitational potential energy. We discuss the nature of the emitted radiation in…
We use a relativistic ray-tracing code to calculate the light curves observed from a global general relativistic magneto-hydrodynamic simulation of an accretion flow onto a Schwarzschild black hole. We apply three basic emission models to…
We present a general relativistic accretion disc model and its application to the soft-state X-ray spectra of black hole binaries. The model assumes a flat, optically thick disc around a rotating Kerr black hole. The disc locally radiates…
Standard accretion disk theory is formulated which is based on the local heat balance. The energy produced by a turbulent viscous heating is supposed to be emitted to the sides of the disc. Sources of turbulence in the accretion disc are…