Related papers: Relativistic disc line: a tool to constrain neutro…
We analysed a dedicated NuSTAR observation of the neutron-star low-mass X-ray binary Z-source GX 13+1 to study the timing and spectral properties of the source. From the colour-colour diagram, we conclude that during that observation the…
The original idea to show the spacetime geometry using few geodesics was developed by Johnson and Ruffini (1974). We used this idea to interpret the observational data for rotating BH's. We developed the imitation approach to simulate a…
In this paper we discuss the spin-equilibrium of accreting neutron stars in LMXBs. We demonstrate that, when combined with a naive spin-up torque, the observed data leads to inferred magnetic fields which are at variance with those of…
Spin of an accreting black hole can be determined by spectroscopy of the emission and absorption features produced in the inner regions of an accretion disc. We discuss the method employing the relativistic line profiles of iron in the…
We present an analysis of XMM-Newton observations of eleven Seyfert galaxies that appear to be missing a broad iron K alpha line. These objects represent a challenge to the established paradigm for active galactic nuclei, where a relatively…
The dust properties of the line-of-sight materials in neutron star low-mass X-ray binaries (LMXBs) can be probed by X-ray observations and laboratory experiments. We use a Markov chain Monte Carlo (MCMC) method to conduct a spectral…
Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely relativistic iron line (Porquet & Reeves 2003). It has been observed twice by XMM-$Newton$, three and half years apart (July 2000 and December 2003). In the second…
The relativistically broadened Fe K$\alpha$ line, originating from the accretion disc in a vicinity of a super massive black hole, is observed in only less than 50\% of type 1 Active Galactic Nuclei (AGN). In this study we investigate could…
Dipping neutron star low-mass X-ray binaries (NS LMXBs) are systems that exhibit periodic drops in their X-ray light curves. These are believed to be caused by material at the impact point of the gas stream onto the accretion disk, the…
Broad Fe K emission lines have been widely observed in the X-ray spectra of black hole systems, and in neutron star systems as well. The intrinsically narrow Fe K fluorescent line is generally believed to be part of the reflection spectrum…
We report on an observation of the neutron star low-mass X-ray binary Serpens X-1, made with NuSTAR. The extraordinary sensitivity afforded by NuSTAR facilitated the detection of a clear, robust, relativistic Fe K emission line from the…
We present Fe Kalpha line profiles from and images of relativistic discs with finite thickness around a rotating black hole using a novel code. The line is thought to be produced by iron fluorescence of a relatively cold X-ray illuminated…
XMM-Newton observations of type I AGN are presented. The properties of the iron K emission line are reviewed, the majority of AGN observed by XMM-Newton show narrow, unresolved (by XMM) iron lines at 6.4 keV from cold matter that must…
An intrinsically narrow line emitted by an accretion disk around a black hole appears broadened and skewed as a result of the Doppler effect and gravitational redshift. The fluorescent iron line in the X-ray band at 6.4-6.9keV is the…
We study the K-correction for the case of emission lines formed in the X-ray illuminated atmosphere of a Roche lobe filling star. We compute the K-correction as function of the mass ratio 'q' and the disc flaring angle 'alpha' using a…
The determination of fundamental parameters in low-mass X-ray binaries typically relies on measuring the radial velocity curve of the companion star through optical or near-infrared spectroscopy. It was recently suggested that high…
Neutron star (NS) radius measurements provide precious information to constrain the dense matter equation of state (EOS). Quiescent low-mass X-ray binaries (qLMXBs) have been used for this purpose, but a number of sources of systematic…
The iron K$\alpha$ line commonly observed in the X-ray spectrum of both stellar-mass and supermassive black hole candidates is produced by the illumination of a cold accretion disk by a hot corona. In this framework, the activation of a new…
We perform the first reflection study of the soft X-ray transient and Type 1 burst source XTE J1709-267 using NuSTAR observations during its 2016 June outburst. There was an increase in flux near the end of the observations, which…
(abridged) With most physicists and astrophysicists in agreement that black holes do indeed exist, the focus of astrophysical black hole research has shifted to the detailed properties of these systems. Nature has provided us with an…