Iron lines from transient and persisting hot spots on AGN accretion disks

Abstract

[abridged] We model the X-ray reprocessing from a strong co-rotating flare above an accretion disk in active galactic nuclei. We explore the horizontal structure and evolution of the underlying hot spot. To obtain the spectral evolution seen by a distant observer, we apply a general relativity ray-tracing technique. We concentrate on the energy band around the iron K-line, where the relativistic effects are most pronounced. Persistent flares lasting for a significant fraction of the orbital time scale and short, transient flares are considered. In our time-resolved analysis, the spectra recorded by a distant observer depend on the position of the flare/spot with respect to the central black hole. If the flare duration significantly exceeds the light travel time across the spot, then the spot horizontal stratification is unimportant. On the other hand, if the flare duration is comparable to the light travel time across the spot radius, the lightcurves exhibit a typical asymmetry in their time profiles. The sequence of dynamical spectra proceeds from more strongly to less strongly ionized re-emission. At all locations within the spot the spectral intensity increases towards edge-on emission angles, revealing the limb brightening effect. Future X-ray observatories with significantly larger effective collecting areas will enable to spectroscopically map out the azimuthal irradiation structure of the accretion disk and to localize persistent flares. If the hot spot is not located too close to the marginally stable orbit of the black hole, it will be possible to probe the reflecting medium via the sub-structure of the iron K-line. Indications for transient flares will only be obtained from analyzing the observed lightcurves on the gravitational time scale of the accreting supermassive black hole.

arXiv comment15 pages, 8 figures, accepted by Astronomy & Astrophysics

References in corpus (36)

• A light bending model for the X-ray temporal and spectral properties of accreting black holes
• The Formation and Structure of a Strongly Magnetized Corona above Weakly Magnetized Accretion Disks
• A Model for the X-Ray and UV Emission from Seyfert Galaxies and Galactic Black Holes
• A long hard look at MCG-6-30-15 with XMM-Newton
• XMM-EPIC observation of MCG-6-30-15: Direct evidence for the extraction of energy from aspinning black hole?
• An extended scheme for fitting X-ray data with accretion disk spectra in the strong gravity regime
• Thermal Instability and Photoionized X-ray Reflection in Accretion Disks
• X-ray Reflection By Photoionized Accretion Discs
• On the Vertical Structure of Radiation-Dominated Accretion Disks
• The Fragmentation of Pre-enriched Primordial Objects
• Flux and energy modulation of redshifted iron emission in NGC3516: implications for the black hole mass
• Effects of Kerr Spacetime on Spectral Features from X-Ray Illuminated Accretion Discs
• Variation of the broad X-ray iron line in MCG-6-30-15 during a flare
• A Chandra HETGS Spectral Study of the Iron K Bandpass in MCG-6-30-15: A Narrow View of the Broad Iron Line
• The structure and radiation spectra of illuminated accretion discs in AGN. I. Moderate illumination
• Mapping the inner regions of MCG-6-30-15 with XMM-Newton
• The strength and width of Fe Kalpha lines in Seyferts and their correlations with the X-ray slope
• Vertical Structure of Accretion Discs with Hot Coronae in AGN
• The structure and radiation spectra of illuminated accretion disks in AGN. II. Flare/spot model of X-ray variability
• Evidence for Orbital Motion of Material Close to the Central Black Hole of Mrk 766
• Escape probability methods versus "exact" transfer for modelling the X-ray spectrum of Active Galactic Nuclei and X-ray binaries
• Surface Structure in an Accretion Disk Annulus with Comparable Radiation and Gas Pressure
• Statistics of relativistically broadened Fe K-alpha lines in AGN
• Variable iron-line emission near the black hole of Markarian 766
• Evolution of the X-ray spectrum in the flare model of Active Galactic Nuclei
• Reflected Iron Line From a Source Above a Kerr Black Hole Accretion Disc
• On time-dependent X-ray reflection by photoionized accretion disks: implication for Fe K-alpha line reverberation studies of AGN
• The response of the Fe Kαline to changes in the X-ray illumination of accretion discs
• The structure and X-ray radiation spectra of illuminated accretion disks in AGN. III. Modeling fractional variability
• Correlated modulation between the redshifted Fe K alpha line and the continuum emission in NGC 3783
• Flare-induced fountains and buried flares in AGN
• Simultaneous X-ray and Ultraviolet spectroscopy of the Seyfert galaxy NGC 5548. III. X-ray time variability
• Exploring the X-ray spectral variability of MCG-6-30-15 with XMM-Newton
• Anisotropic X-ray emission in AGN accretion discs
• Modeling time delays in the X-ray spectrum of the Seyfert galaxy MCG-6-30-15
• Magnetic flares in Active Galactic Nuclei: Modeling the iron Kalpha-line

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