X-ray variability of AGN and correlations with spectral properties

Abstract

Rapid flux changes in the X-ray emission from active galactic nuclei are commonly observed. The power-density spectra show a pseudo power-law form with a turnover at low frequencies and a high frequency break, similar to galactic black-hole candidates. There have been a few claims for periodicities but these are not a well-established property of the class. The amplitude of variability depends on a number of source parameters, including luminosity and spectral properties. The variability amplitude is correlated with X-ray spectral index, and anti-correlated with the width of the permitted optical lines. In one particularly well-observed case, NGC 7469, we see a relationship between the X-ray and UV variability, which indicates that the dominant emission process for the X-rays is thermal Comptonization. Variations in the X-ray emission are related to changes in the UV seed photons, but it appears there must also be a mechanism - perhaps that which heats the Comptonizing corona - that induces rapid variability intrinsic to the X-rays.

12 pages, 6 figures, to appear in Advances in Space Research

References in corpus (1)

• Temporal characteristics of the X-ray emission of NGC 7469

Cited by in corpus (15)

• The properties of the AGN torus as revealed from a set of unbiased NuSTAR observations
• XMM-Newton X-ray study of early type stars in the Carina OB1 association
• XMM-Newton observations of Broad FeKalpha emission from a Seyfert 1.9 galaxy MCG-5-23-16
• A 10-day ASCA Observation of the Narrow-line Seyfert~1 galaxy IRAS 13224-3809
• Exact solution for the Green's function describing time-dependent thermal Comptonization
• Highly variable AGN from the XMM-Newton Slew Survey
• SDSS J075101.42+291419.1: A Super-Eddington Accreting Quasar with Extreme X-ray Variability
• X-ray polarimetric signatures induced by spectral variability in the framework of the receding torus model
• Reflection at large distance from the central engine in Seyferts
• The lively accretion disk in NGC 2992. II. The 2019/2021 X-ray monitoring campaigns
• AstroSat view of spectral transition in the changing-look active galaxy NGC1566 during the declining phase of the 2018 outburst
• Characterisation of the X-ray point source variability in the eROSITA south ecliptic pole field
• Modelling the energy dependent X-ray variability of Mrk 335
• Evidence for coronal temperature variation in Seyfert 2 ESO 103--035 using NuSTAR observations
• A broadband X-ray study of a sample of AGNs with [OIII] measured inclinations