Related papers: Dynamical Comptonization in spherical flows: black…
Evolution of gravitational perturbations, both in time and frequency domains, is considered for a spherically symmetric black hole in the non-reduced Einstein-Aether theory. It is shown that real oscillation frequency and damping rate are…
We investigated accretion on to black holes in presence of viscosity and cooling, by employing an equation of state with variable adiabatic index and multi-species fluid. We obtained the expression of generalized Bernoulli parameter which…
I present results from numerical simulations of gas dynamics outside luminous accretion disks in active galactic nuclei. The gas, gravitationally captured by a super massive black hole, can be driven away by the energy and momentum of the…
By solving radiative transfer equations, we examine three-dimensional radiative properties of a magnetohydrodynamic accretion flow model confronting with the observed spectrum of Sgr A*, in the vicinity of supermassive black hole at the…
Steady, spherically symmetric, adiabatic accretion and wind flows around non-rotating black holes were studied for fully ionized, multi-component fluids, which are described by a relativistic equation of state (EoS). We showed that the…
Accretion onto supermassive black holes powers the most luminous persistent sources in the Universe, the so-called active galactic nuclei, whose emission is characterized by two distinct spectral components: thermal optical/ultraviolet…
The topologies are obtained for accretion flows around black holes as the parameters, accretion rate and specific angular momentum are varied. Paczy{\'n}ski-Wiita pseudo-Newtonian potential is used to mimic the gravitational field of a…
Understanding the dynamics behind black hole state transitions and the changes they reflect in outbursts has become long-standing problem. The X-ray reflection spectrum describes the interaction between the hard X-ray source (the power-law…
We study the role of adiabatic index in determining the critical points in the transonic low angular momentum accretion flow onto a black hole. We present the general relativistic 2D hydrodynamic simulations of axisymmetric, inviscid…
Conformal invariance can ameliorate or eliminate the singularities residing in the black holes, and may still exist in the strong gravity regimes close to these black holes. In this paper, we try to probe this conformal invariance by…
We report on next phase of our study of rotating accretion flows onto black holes. We consider hydrodynamical (HD) accretion flows with a spherically symmetric density distribution at the outer boundary but with spherical symmetry broken by…
In this work we derive simple closed-form expressions for the dynamical friction acting on black holes moving through ultralight (scalar field) dark matter, covering both non-relativistic and relativistic black hole speeds. Our derivation…
Recent advances in the X-ray and soft gamma-ray observations of accreting black holes and microquasars, in particular, are reviewed. The radiative processes responsible for the emission are discussed briefly. The hybrid thermal/nonthermal…
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…
This paper deals with the steady-state polytropic fluid accretion onto a higher-dimensional Reissner-Nordstr$\ddot{o}$m black hole. We formulate the generalized mass flux conservation equation, energy flux conservation and relativistic…
The aim of this work is to improve understanding of the resonant spectra of black holes under perturbations arising from e.g. compact objects or accretion disks in their vicinity. It is known that adding a weak perturbation to the radial…
The structure of the inner edge of the accretion disk around a black hole can be altered, if the matter inside the marginally stable orbit is magnetically connected to the disk. In this case, a non-zero torque is exerted on its inner edge,…
We utilize three complementary approaches to pinpoint the exact form of scattering amplitudes in Schwarzschild spacetime. First, we solve the Regge-Wheeler equation perturbatively in the small-frequency regime. We use the obtained solutions…
The evolution of the mass of a black hole embedded in a universe filled with dark energy and cold dark matter is calculated in a closed form within a test fluid model in a Schwarzschild metric, taking into account the cosmological evolution…
Using full general relativistic calculations, we investigate the possibility of generation of mass outflow from spherical accretion onto non-rotating black holes. Introducing a relativistic hadronic-pressure-supported steady, standing,…