Related papers: Sustaining a Warm Corona in Active Galactic Nuclei…
X-ray reverberation in Active Galactic Nuclei, believed to be the result of the reprocessing of coronal photons by the underlying accretion disc, has allowed us to probe the properties of the inner-most regions of the accretion flow and the…
Relativistically blurred reflection from the accretion disc provides a powerful probe of the extreme environments close to supermassive black holes; the inner regions of the accretion flow and the corona that produces the intense X-ray…
Recently X-ray observations have shown the common presence of compact galactic coronae around intermediate-mass spheroid galaxies embedded in the intracluster/intragroup medium (ICM). We conduct 2-D hydrodynamic simulations to study the…
The magnitude of the viscosity and magnetic field parameters in hot accretion flows is investigated in low luminosity active galactic nuclei (LLAGNs). Theoretical studies show that a geometrically thin, optically thick disk is truncated at…
Data derived from general relativistic magnetohydrodynamic simulations of accretion onto black holes can be used as input to a postprocessing scheme that predicts the radiated spectrum. Combining a relativistic Compton scattering radiation…
We examine all possible stationary, optically thick, geometrically thin accretion disc models relevant for active galactic nuclei (AGN) and identify the physical regimes in which they are stable against the thermal-viscous hydrogen…
A simple model for the X-ray weakness of JWST-selected broad-line AGNs is proposed under the assumption that the majority of these sources are fed at super-Eddington accretion rates. In these conditions, the hot inner corona above the…
Turbulence in an accretion disk launches Alfv\'en waves (AWs) that propagate away from the disk along magnetic field lines. Because the Alfv\'en speed varies with distance from the disk, the AWs undergo partial non-WKB reflection, and…
Recent simulations have demonstrated the formation of 'flux-frozen' and hyper-magnetized disks, qualitatively distinct from both classical $\alpha$ disks and magnetically-arrested disks, as a natural consequence of fueling gas to…
The formation of a cool disk in the innermost regions of black hole X-ray transient systems in the low hard state is investigated. Taking into account the combined cooling associated with the Compton and conductive energy transport…
We report the discovery of a luminous ultra-soft X-ray excess in a radio-loud narrow-line Seyfert1 galaxy, RXJ1633+4718, from archival ROSAT observations. The thermal temperature of this emission, when fitted with a blackbody, is as low as…
We investigate the spectral features of accretion flows composed of an outer cool, optically thick disk and inner hot, optically thin, advection dominated accretion flows (ADAF) within the framework of disk and corona with mass evaporation…
Nuclear reactions occurring deep in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature >5e7 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot…
Recent cosmological simulations have shown that turbulence should be generally prevailing in clusters because clusters are continuously growing through matter accretion. Using one-dimensional hydrodynamic simulations, we study the heating…
Warm Comptonization models for the soft X-ray excess in AGN do not self-consistently explain the relationship between the Comptonizing medium and the underlying accretion disc. Because of this, they cannot directly connect the fitted…
The properties of slim accretion disks, while crucial for our understanding of black hole growth, have yet to be studied extensively observationally. We analyze the multi-epoch broad-band spectral energy distribution of the changing-look…
The primary X-ray emission in active galactic nuclei (AGNs) is widely believed to be due to Comptonisation of the thermal radiation from the accretion disc in a corona of hot electrons. The resulting spectra can, in first approximation, be…
Using a non-linear Monte-Carlo code we investigate the radiative response of an accretion disk corona system to static homogeneous flares. We model a flare by a rapid (comparable to the light crossing time) energy dissipation in the corona…
Active galactic nuclei (AGN) are powerful sources of panchromatic radiation. All AGN emit in X-rays, contributing around $\sim 5-10\%$ of the AGN bolometric luminosity. The X-ray emitting region, popularly known as the corona, is…
Warm absorbers are found in many AGN and consist of clouds moving at moderate radial velocities, showing complex ionization structures and having moderate to large column densities. Using 1D numerical calculations, we confirm earlier…