Related papers: X-ray Emissions from Three-dimensional Magnetohydr…
We report a time averaged 2--8 keV X-ray polarization degree (PD) of $8.5\pm 1.6\%$ ($>3 \sigma$ detection) from the accretion-disc-corona (ADC) neutron-star system 2S 0921-630 (=V395 Car) observed with the Imaging X-ray Polarimetry…
Using a Monte Carlo ray-tracing code in full general relativity, we calculate the transport of photons from a geodesic hot spot emitter through a corona of hot electrons surrounding a black hole. Each photon is followed until it is either…
In this study, we present novel calculations of X-ray polarization from radio-quiet and unobscured active galactic nuclei (AGNs) using the Monte Carlo code MONK, which includes all general and special relativity effects. Our geometric…
We construct a simple model for a magnetic reconnection heated corona above a thin accretion disk in AGNs and Galactic black hole candidates(GBHCs). The basic assumptions are that (1) the magnetic reconnection heat is cooled down…
We investigate the iron K$\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray…
The origin of the soft X-ray excess below 2 keV in active galactic nuclei (AGNs) remains debated, with relativistic reflection from the inner accretion disk and warm Comptonization in an optically thick corona being the leading…
We use a multi-dimensional Monte Carlo code to compute X-ray spectra for a variety of active galactic nucleus (AGN) disk-wind outflow geometries. We focus on the formation of blue-shifted absorption features in the Fe K band and show that…
We compile a sample consisting of 56 radio-quiet active galactic nuclei so as to investigate statistical properties of hot corona of accretion disks from {\em ASCA} observations. The black-hole masses in the sample are estimated via several…
Stellar-mass black holes in x-ray binary systems are powered by mass transfer from a companion star. The accreted gas forms an accretion disk around the black hole and emits x-ray radiation in two distinct modes: hard and soft state. The…
The phenomenology of accretion disc, coronnae and jets in X-ray binaries is rather well established. However the structure of the accretion flow in the various spectral states is still debated and the connection between the hot flow and…
X-ray observations suggest high compactness of coronae in active galactic nuclei as well as in X-ray binaries. The compactness of the source implies a strong radial dependence in the illumination of the accretion disc. This will, for any…
The structure of the accretion flow onto supermassive black holes (SMBH) is not well understood. Standard disc models match to zeroth order in predicting substantial energy dissipation within optically-thick material producing a…
The predictions of the two-phase accretion disc-corona models for active galactic nuclei are compared with observations. We discuss the possibility to use X-ray spectral slopes, equivalent widths of the iron line, and the observed…
We use three-dimensional magnetohydrodynamical (MHD) simulations to study the formation of a corona above an initially weakly magnetized, isothermal accretion disk. We also describe a modification to time-explicit numerical algorithms for…
We consider two phase accretion disk-corona models for active galactic nuclei and some X-ray binaries. We describe in detail how one can exactly solve the polarized radiative transfer and Comptonization using the iterative scattering…
Recent progress in observations and understanding of spectra of Seyfert Galaxies shows that X-rays are most likely produced by magnetic flares on the surface of the disk, similar to Solar X-ray emission. However, while the model reproduces…
The origin of core radio emission in radio-quiet active galactic nuclei (AGNs) is still actively debated. General relativistic magnetohydrodynamics simulations often predict the launching of moderately large-scale jets from super-Eddington…
We use the publicly available XMM-Newton archive to select a sample of 20 active galactic nuclei (AGN) known to exhibit reverberation signatures caused by the reflection of X-rays from the corona off the accretion disc that feeds the…
Hard X-ray emission in radio-quiet active galactic nuclei (AGNs) is believed to be produced via inverse Compton scattering by hot and compact coronae near the super massive black hole. However the origin and physical properties of the…
Energetic X-ray radiations emitted from various accretion systems are widely considered to be produced by Comptonization in the hot corona. The corona and its interaction with the disc play an essential role in the evolution of the system…