Related papers: Energy-dependent variability from accretion flows
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 develop a Monte-Carlo code to compute the Compton scattered X-ray flux arising from a hot inner flow which undergoes Lense-Thirring precession. The hot flow intercepts seed photons from an outer truncated thin disk. A fraction of the…
We present global radiation GRMHD simulations of strongly magnetized accretion onto a spinning, stellar mass black hole at sub-Eddington rates. Using a frequency-dependent Monte Carlo procedure for Compton scattering, we self-consistently…
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…
We analyse the spectra of the archival XMM-Newton data of the Seyfert 1 AGN Zw 229.015 in the energy range $0.3 - 10.0$ keV. When fitted with a simple power-law, the spectrum shows signatures of weak soft excess below 1.0 keV. We find that…
We have used a model of magnetic accretion to investigate the accretion flows of magnetic cataclysmic variables. Numerical simulations demonstrate that four types of flow are possible: discs, streams, rings and propellers. The fundamental…
We derive analytical expressions for the mass flow rates in and from accretion discs, taking into account the Eddington limit. This allows us to connect the basic properties of outflows with those of the accretion flow. As an example, we…
Context: Quasar variability can potentially unlock crucial insights into the accretion process. Understanding how this variability is influenced by wavelength is crucial for validating and refining quasar variability models. Aims: This…
In accretion systems, outflows may have significant influence on the luminosity fluctuations. In this paper, following the Lyubarskii's general scheme, we revisit the power spectral density of luminosity fluctuations by taking into account…
(Abridged) Recent XMM-Newton studies of X-ray variability in the hard states of black hole X-ray binaries (BHXRBs) imply that the variability is generated in the 'standard' optically-thick accretion disc. The variability originates in the…
Numerical simulations of hot accretion flow have shown that the mass accretion rate decreases with decreasing radius; consequently the density profile of accretion flow becomes flatter compared to the case of a constant accretion rate. This…
A phenomenological model of X-ray variability of accreting black holes is considered, where the variable emission is attributed to multiple active regions/perturbations moving radially towards the central black hole. The hard X-rays are…
While many vibrational Raman spectroscopy studies of liquid water have investigated the temperature dependence of the high-frequency O-H stretching region, few have analyzed the changes in the Raman spectrum as a function of temperature…
It has long been thought that black hole accretion flows are driven by magnetohydrodynamic (MHD) turbulence, and there are now many general relativistic global simulations illustrating the dynamics of this process. However, many challenges…
By analyzing the time series of RXTE/PCA data, the nonlinear variabilities of compact sources have been repeatedly established. Depending on the variation in temporal classes, compact sources exhibit different nonlinear features. Sometimes…
Bulk velocities exceed thermal velocities for sufficiently radiation pressure dominated accretion flows. We model the contribution of bulk Comptonization to the soft X-ray excess in AGN. Bulk Comptonization is due to both turbulence and the…
Black holes may accrete gas with angular momentum vectors misaligned with the black hole spin axis. The resulting accretion disks are subject to Lense-Thirring precession, and hence torque. Analytical calculations and simulations show that…
We extend the model of King et al. (2004) for variability in black hole accretion discs, by taking proper account of the thermal properties of the disc. Because the degree of variability in the King et al. (2004) model depends sensitively…
The frequency spectra of the entropy and kinetic energy along with the power spectrum of the thermal flux are computed from direct numerical simulations for turbulent Rayleigh-B\'{e}nard convection with uniform rotation about a vertical…
Based on a unified description of various accretion flows, we find a long-ignored solution - the effectively optically thin accretion flow, occurring at accretion rates around Eddington value. As a consequence of radiation-pressure…