Related papers: Relativistic viscous accretion flow model for ULX …
We study the global accretion-ejection solutions around a rotating black hole considering three widely accepted pseudo-Kerr potentials that satisfactorily mimic the space-time geometry of rotating black holes. We find that all the pseudo…
A sub-set of the brightest ultraluminous X-ray sources (ULXs), with X-ray luminosities well above $10^{40}$ erg s$^{-1}$, typically have energy spectra which can be well described as hard power-laws, and short-term variability in excess of…
We investigated the instability of advective accretion flow as a consequence of angular momentum transfer in one-dimensional, quasi-spherical transonic accretion flow around a non-rotating black hole. The code is designed to include the…
We investigate the dependence of the viewing angle in supercritical accretion flows and discuss the observational implications of galactic black-hole candidates and ultraluminous X-ray sources. When the mass accretion rate exceeds the…
The nature of ultraluminous X-ray sources (ULXs) is presently unknown. A possible explanation is that they are accreting intermediate mass black holes (IBHs) that are fed by Roche lobe overflow from a tidally captured stellar companion. We…
We present new radio, optical, and X-ray observations of three Ultraluminous X-ray sources (ULXs) that are associated with large-scale nebulae. We report the discovery of a radio nebula associated with the ULX IC342 X-1 using the Very Large…
We develop and discuss a model formalism to study the properties of mass outflows that are emerged out from a relativistic, magnetized, viscous, advective accretion flow around a rotating black hole. In doing so, we consider the toroidal…
We study the relativistic accretion flow around a generic stationary axisymmetric space-time and obtain an effective potential ($\Phi^{\rm eff}$) that accurately mimics the general relativistic features of Kerr black hole having spin $0\le…
Evidence is mounting that some Ultra-luminous X-ray sources (ULXs) may contain accreting intermediate-mass black holes (IMBHs). We review the current observational evidence for IMBH-ULXs. While low-luminosity ULXs with L_X <~ 10^39.5 erg/s…
We investigate outflows and the physics of super-Eddington versus sub-Eddington regimes in black hole systems. Our focus is on prospective science using next-generation high-resolution soft X-ray instruments. We highlight the properties of…
Ultraluminous X-ray sources (ULXs) are bright extragalactic sources with X-ray luminosities above 10^39 erg/s powered by accretion onto compact objects. According to the first studies performed with XMM-Newton ULXs seemed to be excellent…
Accretion flows having low angular momentum and low viscosity can have standing shock waves. These shocks arise due to the presence of multiple sonic points in the flow. We study the region of the parameter space in which multiple sonic…
We show that black holes supplied with mass at hyper--Eddington rates drive outflows with mildly sub--relativistic velocities. These are $\sim 0.1 - 0.2c$ for Eddington accretion factors $\dot m_{\rm acc} \sim 10 - 100$, and $\sim…
We examine radiative standing shocks in advective accretion flows around stellar-mass black holes by 2D radiation hydrodynamic simulations, focusing on the super-Eddington accreting flow. Under a set of input flow parameters responsible for…
It is thought that ultraluminous X-ray sources (ULXs) are mainly powered by super-Eddington accreting neutron stars or black holes as shown by recent discovery of X-ray pulsations and relativistic winds. This work presents a follow up study…
NGC 1313\,X-1 is a mysterious Ultra-luminous X-ray (ULX) source whose X-ray powering mechanism and a bubble-like structure surrounding the source are topics of intense study. Here, we perform the X-ray spectroscopic study of the source…
Type-C QPOs in X-ray binaries have been often interpreted as a consequence of relativistic Lense-Thirring precession around a spinning black hole and they potentially offer a way to measure black hole spins and masses. The connection…
Relativistic reflection features in the X-ray spectra of accreting black holes are considered to be generated by the illumination of the accretion disk by the hot corona. In this work, we present a numerical method for the emission line…
By performing a viscous hydrodynamics simulation in general relativity for super-Eddington accretion flows onto massive black holes of mass $M=10^5$--$10^7M_\odot$, we discuss a formation scenario for black hole-envelope systems. We…
We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic stellar-mass black hole binaries. The detection of coherent…