Related papers: Relativistic Accretion Mediated by Turbulent Compt…
Matter falling onto black holes is hot, fully ionized and has to be necessarily transonic. Since the electrons are responsible for radiative cooling via processes like synchrotron, bremsstrahlung and inverse-Compton, therefore the electron…
We show that Compton scattering of soft photons with energies near 100 eV in thermally stratified black-hole accretion plasmas with temperatures in the range 100 keV - 1 MeV can give rise to an X-ray spectral hardening near 10 keV. This…
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…
The hard X-ray emission observed in accreting compact sources is believed to be produced by inverse Compton scattering of soft photons arising from the accretion disc by energetic electrons thermally distributed above the disc, the…
Traditionlly, gravitational wave emission from a coalescing binary system is computed using point mass approximations without considering any accretion disk. However, it is believed that in many of the galactic nuclei, there are…
Significant fraction of matter in supercritical (or super-Eddington) accretion flow is blown away by radiation force, thus forming outflows, however, the properties of such radiation-driven outflows have been poorly understood. We have…
Inverse Compton scattering by the thermal motions of electrons is believed to produce polarized hard X-rays in active galactic nuclei and black-hole binaries. Meanwhile, plasma within the plunging region of the black hole free falls into…
Ultraluminous X-ray sources (ULXs) are extreme X-ray binaries shining above 10^39 erg/s, in most cases as a consequence of super-Eddington accretion onto neutron stars and stellar-mass black holes accreting above their Eddington limit. This…
The hot inner flow in black-hole X-ray binaries is not just a static corona rotating around the black hole, but it must be partially outflowing. We have developed a model, in which Comptonization takes place in this outflowing corona. We…
In this work, we measure two important phenomenological parameters of corona (and hot accretion flow) in black hole X-ray binaries: the photon index $\Gamma$ and the electron temperature $\te$. Thanks to the capability of {\it NuSTAR} in…
Most astrophysical sources powered by accretion onto a black hole, either of stellar mass or supermassive, when observed with hard X-rays show signs of a hot Comptonizing component in the flow, the so-called corona, with observed…
The quasi-steady structure of super-critical accretion flows around a black hole is studied based on the two-dimensional radiation-hydrodynamical (2D-RHD) simulations. The super-critical flow is composed of two parts: the disk region and…
The corona is a key component of most luminous accreting black holes, carrying 5 - 30 % of the power and in non-jetted Active Galactic Nuclei (AGN), creating all the X-ray emission above $\simeq 1-2$ keV. Its emission illuminates the inner…
All sufficiently massive clusters of galaxies are expected to be surrounded by strong accretion shocks, where protons can be accelerated to $\sim 10^{18}$-$10^{19}$ eV under plausible conditions. Such protons interact with the cosmic…
We extended the disk corona model (Meyer & Meyer-Hofmeister 1994; Meyer, Liu, & Meyer-Hofmeister 2000a) to the inner region of galactic nuclei by including different temperatures in ions and electrons as well as Compton cooling. We found…
In some Seyfert Galaxies, the hard X-rays that produce fluorescent emission lines are thought to be generated in a hot corona that is compact and located at only a few gravitational radii above the supermassive black hole. We consider the…
The time dependent evolution of the accretion disk around black hole is computed. The classical description of the $\alpha$-viscosity is adopted so the evolution is driven by the instability operating in the innermost radiation-pressure…
The geometry of the accretion flow around stellar-mass black holes can change on timescales of days to months. When a black hole emerges from quiescence (that is, it "turns on" after accreting material from its companion) it has a very hard…
The standard thin accretion disc model predicts that discs around stellar mass black holes become radiation pressure dominated and thermally unstable once their luminosity exceeds L>0.02 L_Edd. Observationally, discs in the high/soft state…
Existence of relatively cool ($k_B T \lesssim 10~{\rm keV}$) and optically thick ($\tau \gtrsim 3$) coronae are inferred above super-Eddington accretion flow such as ultraluminous X-ray sources (ULXs), GRS 1915+105, and narrow-line Seyfert…