1,721,468 research outputs found
On the origin of the broad, relativistic iron line of MCG-6-30-15 observed by XMM-Newton
No full textThe relativistic iron line profile recently observed by XMM-Newton in the spectrum of the Seyfert 1 galaxy MCG-6-30-15 (Wilms et al. 2001) is discussed in the framework of the lamp-post model. It is shown that the steep disc emissivity, the large line equivalent width and the amount of Compton reflection can be self-consistently reproduced in this scenario
Effects of Kerr space-time on spectral features from X-ray illuminated accretion discs
No full textWe performed detailed calculations of the relativistic effects acting on both the reflection continuum and the iron line from accretion discs around rotating black holes. Fully relativistic transfer of both illuminating and reprocessed photons has been considered in Kerr space-time. We calculated overall spectra, line profiles and integral quantities, and present their dependences on the black hole angular momentum. We show that the observed EW of the lines is substantially enlarged when the black hole rotates rapidly and/or the source of illumination is near above the hole. Therefore, such calculations provide a way to distinguish between different models of the central source
Polarization signatures of strong gravity in active galactic nuclei accretion discs
No full textThe effects of strong gravity on the polarization of the Compton reflection from an X-ray-illuminated accretion disc are studied. The gravitational field of a rotating black hole influences Stokes parameters of the radiation along the propagation to a distant observer. Assuming the lamp-post model, the degree and the angle of polarization are examined as functions of the observer's inclination angle, of the height of the primary source and of the inner radius of the disc emitting region. It is shown that polarimetry can provide essential information on the properties of black holes sources, and it is argued that time variation of the polarization angle is a strong signature of general-relativity effects. The expected polarization degree and angle should be detectable by new-generation polarimeters, such as that planned for the Xeus mission
Emission-line profiles from self-gravitating thin disks
No full textWe have constructed general relativistic models of a stationary, axially symmnetric, Keplerian thin disk around a rotating black hole. We computed profiles of a spectral line, emitted in the inner region of the disk. In our models we have taken into account also the self-gravity of the disk. The aim of this work is to study gravitational effects on the line profiles in connection with the X-ray features observed in spectra of active galactic nuclei. In some cases, the calculated profiles are clearly affected by the disk gravity but relativistic dragging effects are found to be negligible
Relativistic features from X-ray illuminated spots in AGN
No full textNarrow spectral features in the 5-6 keV range were recently discovered in the X-ray spectra of a few AGN. We discuss the possibility that these features are redshifted iron lines from orbiting spots on the surface of the accretion disc, and compare numerical models with the observations. If the model is correct, these features can be used to measure the mass of Supermassive Black Holes in Active Galactic Nuclei, a task for future X-ray missions like Constellation-X
Understanding the relativistic accretion disk of GRS 1915+105
No full textWe discuss the evidence for GRS 1915 + 105 hosting an optically thick, relativistic accretion disk (at least in some spectral phases). We give particular emphasis to the iron line phenomenology. (C) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved
Relativistic iron features from X-ray illuminated spots and the measure of the black hole mass in AGN RID B-4804-2010
No full textNarrow spectral features in the 5-6 keV range were recently discovered in the X-ray spectra of a few Active Galactic Nuclei. We propose that these features originate from localized spots occurring on the surface of an accretion disc following its illumination by flares. Detailed calculations of the temporal and spectral properties of these features in our proposed model can be found in Dovciak et al. (2004). Comparison of the computed profiles with observed features can help to estimate parameters of the system. In principle this method can provide a powerful tool to measure the mass of super-massive black holes in Active Galactic Nuclei. By comparing our calculations with the Chandra and XMM-Newton results, we show, however, that spectra from present generation X-ray satellites are not of good enough quality to fully exploit the method and determine the black hole mass with sufficient accuracy. This task has to be deferred to future missions with both large sensitivity and high energy resolution, such as Constellation-X and Xeus
Iron line diagnostics for the GRS 1915+105 black hole
No full textThe properties of the broad Fe line detected in two BeppoSAX observations of the microquasar GRS 1915+105 are summarized
- …
