Related papers: Magnetized transonic accretion disks
We develop a simple physical model to describe the most common type of low-frequency quasi-periodic oscillations (QPOs) seen in a number of accreting black hole systems, as well as the shape of the relativistically broadened iron emission…
Type-C quasi-periodic oscillations (QPOs) are the low-frequency QPOs most commonly observed during the hard spectral state of X-ray binary systems. The leading model for these QPOs is the Lense-Thirring precession of a hot, geometrically…
We study the two-dimensional structure of thin transonic accretion discs in the vicinity of black holes. We use the hydrodynamical version of the Grad-Shafranov equation and focus on the region inside the marginally stable orbit. We show…
Spherically symmetric transonic accretion of a fractal medium has been studied in both the stationary and the dynamic regimes. The stationary transonic solution is greatly sensitive to infinitesimal deviations in the outer boundary…
We propose a unified model to explain Quasi-Periodic-Oscillation (QPO), particularly of high frequency, observed from black hole and neutron star systems globally. We consider accreting systems to be damped harmonic oscillators exhibiting…
Classical black hole analogues (alternatively, the analogue systems) are fluid dynamical analogue of general relativistic black holes. Such analogue effects may be observed when acoustic perturbations (sound waves) propagate through a…
Numerical, two-dimensional, time-dependent hydrodynamical models of geometrically thick accretion discs around black holes are presented. Accretion flows with non-effective radiation cooling (ADAFs) can be both convectively stable or…
Qualitative arguments are presented to demonstrate that the energy density of magnetic fields in matter accreting onto a black hole inside the marginally stable orbit is automatically comparable to the rest-mass energy density of the…
We apply the global mode analysis, which has been recently developed for the modeling of kHz quasi-periodic oscillations (QPOs) from neutron stars, to the inner region of an accretion disk around a rotating black hole. Within a…
The global nonlinear time-dependent evolution of the inertial-acoustic mode instability in accretion disks surrounding black holes has been investigated. The viscous stress is assumed to be proportional to the gas pressure only, i.e.\,,…
In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the…
Quasi periodic oscillations (QPO) seen in the X-ray fluxes of individual neutron stars and black hole sources are one of most intriguing phenomena in today's astrophysics. The QPO nature is visibly determined by super-strong Einstein's…
Stationary and axisymmetric ideal magnetohydrodynamic (MHD) accretion onto a black hole is studied analytically. The accreting plasma ejected from a plasma source with low velocity must be super-fast magnetosonic before passing through the…
We conduct a systematic study of the properties of tilted accretion flows around spinning black holes, covering a range of tilt angles and black hole spins, using the general-relativistic magnetohydrodynamics code Athena++. The same initial…
We present the accretion of magnetized supersonic winds onto a rotating black hole in three dimensions. We select representative spin-wind orientations in order to illustrate its effects on the evolution and morphology of the shock cone.…
We numerically investigate the thermally unstable accretion disks around black holes. We adopt an evolutionary viscous stress equation to replace the standard alpha-prescription based on the results of two MHD simulations. We find a kind of…
Viscous Keplerian discs become sub-Keplerian close to a black hole since they pass through sonic points before entering into it. We study the time evolution of polytropic viscous accretion discs (both in one and two dimensional flows) using…
We show that the low frequency QPO seen in the power density spectra of black hole binaries (and neutron stars) can be explained by Lense-Thirring precession. This has been proposed many times in the past, and simple, single radius models…
For the past twenty-five years, nearly all analyses of accretion disk dynamics have assumed that stress inside the disk is locally proportional to pressure (the "alpha-model") and that this stress goes to zero at the marginally stable…
We present the results of global three dimensional magneto-hydrodynamic simulations of black hole accretion flows. We focus on the dependence of numerical results on the gas temperature Tout supplied from the outer region. General…