Related papers: Latest trends in the study of accretion and outflo…
Changing-look phenomenon observed now in a growing number of active galaxies challenges our understanding of the accretion process close to a black hole. We propose a simple explanation for periodic outbursts in sources operating at a few…
Accretion onto black holes often leads to the launch of outflows that significantly influence their surrounding environments. The two primary forms of these outflows are X-ray disk winds-hot, ionized gases ejected from the accretion…
Despite the prevalence of jets in accreting systems and their impact on the surrounding medium, the fundamental physics of how they are launched and collimated is not fully understood. Radio observations of local compact objects, including…
We examine the properties of the outflowing matter from an advective accretion disc around a spinning black hole. During accretion, rotating matter experiences centrifugal pressure supported shock transition that effectively produces a…
Accretion onto supermassive black holes produces both the dramatic phenomena associated with active galactic nuclei and the underwhelming displays seen in the Galactic Center and most other nearby galaxies. I review selected aspects of the…
Recent developments in the spectropolarimetric study of compact objects, specifically black holes (stellar and massive) and neutron stars are reviewed. The lectures are organized around five topics: disks, jets, outflows, neutron stars and…
We investigate advection dominated, transsonic accretion flows in the vicinity of a Kerr black hole. We take into account all relativistic effects in the dynamics of the flow and in the propagation of light. We assume the matter to be…
I review accretion and outflow in active galactic nuclei. Accretion appears to occur in a series of very small--scale, chaotic events, whose gas flows have no correlation with the large--scale structure of the galaxy or with each other. The…
We consider time-dependent models for rotating accretion flows onto black holes, where a transition takes place from an outer cooling-dominated disc to a radiatively inefficient flow in the inner region. In order to allow for a transition…
The phenomenon by which matter accumulates in the vicinity of a huge celestial object is known as accretion. The gravitational energy is excreted as a consequence of infalling matter onto compact objects. The accretion procedure around…
We discuss new observations of X-ray novae which provide strong evidence that black holes have event horizons. Optical observations of 13 X-ray novae indicate that these binary stars contain collapsed objects too heavy to be stable neutron…
We studied the outflow behaviour from accretion discs around black holes taking into account the vertical equilibrium accretion flow model. The outflow rate is found to depend crucially on flow composition. Our approach is to study the…
We model the UV/optical spectrum of the black hole binary Nova Muscae as a sum of black body emissions from the outer region of an accretion disk. We show for self-consistency that scattering effects in this region are not important. The…
According to various models, the orbital and the epicyclic frequencies of particles moving on a circular orbit around compact objects are related to the quasi-periodic oscillations observed in the X-ray flux of some pulsars or black hole…
The outburst cycles of black hole X-ray transients are now generally understood as caused by a thermal instability in the accretion disk, the same mechanism as in dwarf novae outbursts. During quiescence the accretion occurs via a cool disk…
Two component X-ray spectra (soft multicolor black body plus harder power law) are frequently observed from accreting black holes. These components are presumably associated with the different parts of the accretion flow (optically thick…
Accreting black hole sources show variable outflows at different mass scales. For instance, in the case of galactic nuclei, our own galactic center Sgr A* exhibits flares and outbursts in the X-ray and infrared bands. Recent studies suggest…
We study the neutrino scattering off a rotating black hole with a realistic accretion disk permeated by an intrinsic magnetic field. Neutrino trajectories in curved spacetime as well as the particle spin evolution in dense matter of an…
In this paper we examine time-dependent and three-dimensional perturbations of spherical accretion flow onto a neutron star close to its Eddington limit. Our treatment assumes a Schwarzschild geometry for the spacetime outside the neutron…
We investigate the dynamical structure of advective accretion flow around stationary as well as rotating black holes. For a suitable choice of input parameters, such as, accretion rate ($\dot {\cal M}$) and angular momentum ($\lambda$),…