相关论文: Steep X-ray reflection emissivity profiles in AGN …

The study of radiation emitted from black hole accretion discs represents a crucial way to understand the main physical properties of these sources, and in particular the black hole spin. Beside spectral analysis, polarimetry is becoming…

A model for the inner regions of accretion flows is presented where, due to disc instabilities, cold and dense material is clumped into deep sheets or rings. Surrounding these density enhancements is hot, tenuous gas where coronal…

The observation of energetic X-ray emission from black holes, inconsistent with thermal emission from an accretion disk, has long indicated the presence of a "corona" around these objects. However, our knowledge of the geometry,…

Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales,…

We have simultaneously fit Chandra and RXTE spectra of the Galactic black hole XTE J1118+480 with three models for X-ray reflection. We explored a range of accretion disc ionizations (log(xi)=1-4; xi=L_X/nR^{2}) and iron abundances…

We discuss black hole spin measurements employing the relativistic iron line profiles in the X-ray domain. We investigate the iron line band for two representative sources -- MCG -6-30-15 (active galaxy) and GX 339-4 (X-ray binary). We…

In this work, we carry out a new spectral reanalysis of NuSTAR and Suzaku observations of the disk reflection spectra in the stellar-mass black hole X-ray binary Cyg~X-1. We compare three types of models: a broken power-law disk emissivity…

X-ray polarimetry can potentially constrain the unknown geometrical shape of AGN coronae. We present simulations of the X-ray polarization signal expected from AGN coronae, assuming three different geometries, namely slab, spherical and…

Active galactic nuclei (AGN) are powerful sources of panchromatic radiation. All AGN emit in X-rays, contributing around $\sim 5-10\%$ of the AGN bolometric luminosity. The X-ray emitting region, popularly known as the corona, is…

X-ray observations of active galactic nuclei (AGN) show variability on timescales ranging from a few hours up to a few days. Some of this variability may be associated with occultation events by clouds in the broad line region. In this…

Accretion around black holes is very often characterized by distinctive X-ray reflection features (mostly, iron inner-shell transitions), which arise due to the primary radiation being reprocessed by a dense and relatively colder medium,…

Observations of neutral hydrogen in spiral galaxies reveal a sharp cutoff in the radial density profile at some distance from the center. Using 22 galaxies with known HI distributions as an example, we discuss the question of whether this…

Accretion in black hole X-ray binaries is commonly believed to be supplied by the Roche lobe overflow or the stellar wind. The former is thought to form a geometrically thin disc while the diffuse wind could form a geometrically thick hot…

Irradiation of the accretion disc causes reflection signatures in the observed X-ray spectrum, encoding important information about the disc structure and density. A Type I X-ray burst will strongly irradiate the accretion disc and alter…

We propose that the polarization of the emission from the X-ray binary Cygnus X-1, measured using the Imaging X-ray Polarimetry Explorer (IXPE), is imprinted by bulk Comptonization of coronal emission in a mildly relativistic wind or jet…

We model the reflected spectrum expected from localized magnetic flares above an ionised accretion disk. We concentrate on the case of very luminous magnetic flares above a standard accretion disk extending down to the last stable orbit,…

Characteristic signatures that X-ray reverberation from an extended corona can manifest in the observed PSD of AGN are investigated. The presence of two X-ray blobs illuminating an accretion disc can cause the interference between two…

We present spectral calculations of non-LTE accretion disk models appropriate for high luminosity stellar mass black hole X-ray binary systems. We first use a dissipation profile based on scaling the results of shearing box simulations of…

We report results obtained from six XMM-Newton observations of the Seyfert galaxy 1H 0419-577. Here we show that the X-ray spectrum and variability are well described by a two-component model comprising a power law with constant spectral…

Black-hole binary (BHB) systems comprise a stellar-mass black hole and a closely orbiting companion star. Matter is transferred from the companion to the black hole, forming an accretion disk, corona and jet structures. The resulting…