Related papers: Relativistic disc line: a tool to constrain neutro…
Since the discovery of the first broad iron-K line in 1995 from the Seyfert Galaxy MCG--6-30-15, broad iron-K lines have been found in several other Seyfert galaxies, from accreting stellar mass black holes and even from accreting neutron…
The broad iron K$\alpha$ emission line, commonly seen in the X-ray spectrum of Seyfert nuclei, is thought to originate when the inner accretion disk is illuminated by an active disk-corona. We show that relative motion between the disk and…
We have investigated whether the lack of X-ray pulsations from most neutron star (NS) low-mass X-ray binaries (LMXBs) could be due to the extension of their inner disc to the NS surface. To estimate the inner disc radii, we have employed…
We calculate the response of a line emitted from a relativistic accretion disk to a continuum variation of the central illuminating source. This model might be relevant to the very broad and sometimes redshifted emission lines which have…
Observations of AGNs and microquasars by ASCA, RXTE, Chandra and XMM-Newton indicate the existence of broad X-ray emission lines of ionized heavy elements in their spectra. Such spectral lines were discovered also in X-ray spectra of…
Recent observations with Chandra and XMM-Newton, aided by broad-band spectral coverage from RXTE, have revealed skewed relativistic iron emission lines in stellar-mass Galactic black hole systems. Such systems are excellent laboratories for…
Observations of fluorescent iron lines from accreting black holes provide one of the best tests of strong field gravity available to date, and the only current observational tool to probe black hole spacetime. However, the two most widely…
The broad X-ray iron line seen in the spectra of many AGN is thought to originate from the inner regions of the putative black hole accretion disk, and hence provides a rare probe of that central region. In principle, future high throughput…
The spacetime geometry around astrophysical black holes is supposed to be well approximated by the Kerr metric, but deviations from the Kerr solution are predicted in a number of scenarios involving new physics. Broad iron K$\alpha$ lines…
There is still 10-20% uncertainty on the neutron star (NS) mass-radius relation. These uncertainties could be reduced by an order of magnitude through an unambiguous measure of M/R from the surface redshift of a narrow line, greatly…
We present 3-79 keV NuSTAR observations of the neutron star low-mass X-ray binary 4U 1636-53 in the soft, transitional and hard state. The spectra display a broad emission line at 5-10 keV. We applied several models to fit this line: A…
Mid-infrared atomic and ionic line ratios measured in spectra of pre-main sequence stars are sensitive indicators of the hardness of the radiation field impinging on the disk surface. We present a low-resolution Spitzer IRS search for [Ar…
The shape and the intensity of the 6.4 keV iron line bring unique information on the geometrical and physical properties of the supermassive black hole and the surrounding accreting gas at the very center of Active Galactic Nuclei. While…
Petrucci et al. (2002; hereafter P02) have reported extraordinary behaviour of the iron K alpha line in the type 1 AGN Mrk 841. At the XMM-Newton/EPIC resolution, a narrow line was observed in a short observation, which then apparently…
Recent X-ray observations have enabled the study of reverberation delays in AGN for the first time. All the detections so far are in sources with a strong soft excess, and the measured delay is between the hard (1-3 keV) direct continuum…
We confirm the detection of the relativistically broadened iron K-alpha emission at 6.4 keV with simultaneous Chandra HETGS and RXTE PCA observations. Heavily binned HETGS data show a disk line profile with parameters very similar to those…
We present angle-dependent, broad-band intensity spectra from accretion disks around black holes of 10 M$_\odot$. In our computations disks are assumed to be slim, which means that the radial advection is taken into account while computing…
We analysed the XMM-Newton archival observations of 16 neutron star (NS) low-mass X-ray binaries (LMXBs) to study the Fe K emission in these objects. The sample includes all the observations of NS LMXBs performed in EPIC pn Timing mode with…
The fluorescent iron K$\alpha$ emission line profile provides an excellent probe of the innermost regions of active galactic nuclei. Fe XXV and Fe XXVI in diffuse plasma above the accretion disc can affect the X-ray spectrum by iron…
The launch of the Nuclear Spectroscopic Telescope Array (NuSTAR) heralded a new era of sensitive high energy X-ray spectroscopy for X-ray binaries (XRBs). In this paper we show how multiple physical parameters can be measured from the…