Related papers: Iron Line from Neutron Star Accretion Disks in Sca…
We present an analysis of the 101 ks, 2007 Suzaku spectrum of the LINER galaxy NGC 1052. The 0.5-10 keV continuum is well-modeled by a power-law modified by Galactic and intrinsic absorption, and it exhibits a soft, thermal emission…
Spherical neutron star models are studied within tensor-scalar theories of gravity. Particularly, it is shown that, under some conditions on the second derivative of the coupling function and on star's mass, for a given star there exist two…
We report on a 63-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4-3658 during the latest X-ray outburst which started on September 21st 2008. The pn spectrum shows a highly significant emission line in the…
In this paper we present a fully relativistic approach to modelling both the continuum emission and the reflected fluorescent iron line from a primary X-ray source near a Kerr black hole. The X-ray source is located above an accretion disc…
We present a rest-frame spectral stacking analysis of ~1000 X-ray sources detected in the XMM-COSMOS field in order to investigate the iron K line properties of active galaxies beyond redshift z~1. In Type I AGN that have a typical X-ray…
We report on a 133 ks XMM-Newton observation of the Seyfert 1 galaxy Markarian 335. The 0.4-12 keV spectrum contains an underlying power law continuum, a soft excess below 2 keV, and a double-peaked iron emission feature in the 6-7 keV…
Relativistic X-ray disk-lines have been found in multiple neutron star low-mass X-ray binaries, in close analogy with black holes across the mass-scale. These lines have tremendous diagnostic power and have been used to constrain stellar…
We investigate in this paper the structures of neutron stars under the strong magnetic field in the framework of $f(T)$ gravity where $T$ denotes the scalar torsion. The TOV equations in this theory of gravity have been considered and…
We calculate the atmospheric structure of an accretion disk around a Kerr black hole and obtain its X-ray spectrum, which exhibits prominent atomic transitions under certain circumstances. The gravitational and Doppler (red)shifts of the C…
The iron K line is perhaps the most important spectral diagnostic available in the study of accreting black holes. The line is thought to result from the reprocessing of external X-rays by the surface of the accretion disk. However, as is…
The observation of the Narrow-Line Seyfert 1 galaxy IRAS13349+2438 performed by XMM-Newton European Photon Imaging Camera between 0.3-10 keV, is presented here. The broadband spectrum of the source is dominated at low energies (E < 2 keV)…
We present the X-ray spectrum of the broad-line radio galaxy Pictor A as observed by ASCA in 1996. The main objective of the observation was to detect and study the profiles of the Fe~K$\alpha$ lines. The motivation was the fact that the…
Iron K-alpha lines are key diagnostics of the central regions of AGN. Their profiles indicate that they are formed deep in the potential well of the central black hole, where extreme broadening and red shift occur. The profiles are most…
Broad Fe K-alpha emission lines have recently been reported in a number of Galactic black holes. Such lines are useful accretion flow diagnostics because they may be produced at the inner accretion disk and shaped by relativistic effects,…
Scalar-tensor theories are among the most promising alternatives to general relativity that have been developed to account for some long standing issues in our understanding of gravity. Some of these theories predict the existence of a…
We present a new evidence of the accretion disc in active galactic nuclei, by examining the properties of the Ha emission line versus viewing angle, in a sample of superluminal (SL) quasars. Both line velocity width (FWHM) and rest…
We describe a new code which can accurately calculate the relativistic effects which distort the emission from an accretion disc around a black hole. We compare our results for a disk which extends from the innermost stable orbit to…
We study neutron stars in a varying speed of light (VSL) theory of gravity in which the local speed of light depends upon the value of a scalar field $\phi$. We find that the masses and radii of the stars are strongly dependent on the…
Recently, a rotating black hole solution was found in Vector-Tensor Galileons modified gravity that has some significant differences from the Kerr black hole solution. We study the iron line shape that is part of the reflection spectrum of…
If an accretion disk around a black hole is illuminated by hard X-rays from non-thermal coronae, fluorescent iron lines will be emitted from the inner region of the accretion disk. The emission line profiles will show a variety of strong…