相关论文: Iron K-alpha line profiles driven by non-axisymmet…
We analyze X-ray spectra of heavily obscured (N_H > 10^{24} cm^{-2}) active galaxies obtained with Chandra, concentrating on the iron K alpha fluorescence line. We measure very large equivalent widths in most cases, up to 5 keV in the most…
Accreting black holes often show iron line emission in their X-ray spectra. When this line emission is very broad or variable then it is likely to originate from close to the black hole. The theory and observations of such broad and…
We present a detailed analysis of the XMM-Newton long-look of the Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two resolved peaks at 6.4 keV and 7.0 keV, consistent with neutral or near-neutral Fe K alpha and K beta emission.…
Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in galaxies with an X-ray luminosity above 3x10^39 erg/s, thought to be powered by accretion onto a compact object. Possible explanations include accretion onto…
Spectroscopy of X-ray emission lines emitted in accretion discs around supermassive black holes is one of the most powerful probes of the accretion flow physics and geometry, while also providing in principle observational constraints on…
Significant variability in broad emission line strengths of active galactic nuclei (AGN) over months to years has been observed, often accompanied by intrinsic continuum changes. Such spectral variability challenges the traditional AGN…
We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines from…
This paper continues the study of the properties of an accretion disc rotating around a non-baryonic (assumed super-massive) compact object. This kind of objects, generically known as boson stars, were earlier proposed as a possible…
The atomic features in the X-ray spectra of the ultraluminous X-ray source (ULX) may be associated with the outflow (Middleton et al. 2015), which may provide a way to explore the physics of the ULXs. We construct a conical outflow model,…
We present a model for the prediction of the optical/infra-red emission from ULXs. In the model, ULXs are binary systems with accretion taking place through Roche lobe overflow. We show that irradiation effects and presence of an accretion…
The Fe I 6173 {\AA} line is widely used in the measurements of vector magnetic fields by instruments including the Helioseismic and Magnetic Imager (HMI). We perform non-local thermodynamic equilibrium calculations of this line based on…
The nature of the super-massive black hole candidates in galactic nuclei can be tested by analyzing the profile of the K$\alpha$ iron line observed in their X-ray spectrum. In this paper, we consider the possibility that the spacetime in…
In this chapter we discuss the X-ray radiation from relativistic accretion disks around supermassive black holes, supposed to exist in the centers of Active Galactic Nuclei (AGN). Our focus is on the X-ray radiation, especially in the Fe…
The Fe K_\alpha fluorescent line at 6.4 keV is a powerful probe of the space-time metric in the vicinity of accreting compact objects. We investigated here how some alternative theories of gravity, namely Scalar tensor Theories, that invoke…
The observed profile of spectral lines from a relativistic accretion disk can constrain parameters such as the disk geometry and the rotation of the central black hole. The formation of the spectral line in a disk generally has been modeled…
We detect variability of the Fe Ka emission line in the spectrum of X-ray pulsar 4U 1626-67, correlated with changes in its luminosity and in the shape of its pulse profile. Analysis of archival Chandra and RXTE observations revealed the…
A linear relation between absolute rms variability and flux in X-ray observations of compact accreting sources has recently been identified. Such a relation suggests that X-ray lightcurves are non-linear and composed of a lognormal…
We report the observation of a novel nonlinear effect in the hard x-ray range. Upon illuminating Fe and Cu metal foils with intense x-ray pulses tuned near their respective K edges, photons at nearly twice the incoming photon energy are…
The reported observations of an unidentified X-ray line feature at $\sim$3.5 keV have driven a lively discussion about its possible dark matter origin. Motivated by this, we have measured the \emph{K}-shell X-ray spectra of highly ionized…
Flourescent iron line profiles currently provide the best diagnostic for active galactic nuclei (AGN) engine geometries. Here we construct a method for calculating the relativistic iron line profile from an arbitrarily warped accretion…