Ionised Accretion Discs in Active Galactic Nuclei: The Effects of a Lamppost with a Variable Height

Abstract

The X-ray emitting corona irradiates and ionises the surface of the inner accretion disc in Active Galactic Nuclei (AGNs). The ionisation parameter of the inner disc at a radius $r$ from the black hole, $\xi (r)$, can be used to infer information about the location of the corona. Here, a new formula is derived that predicts $\xi (r,h)$ for a disc irradiated by a X-ray source at a height $h$ above the black hole symmetry axis (i.e., a lamppost geometry). The equation is independent of the black hole mass and the X-ray spectrum, and accounts for the effects of gravitational light-bending on the ionisation state and a variable coronal dissipation factor. We predict a strong ionisation gradient across the surface of the inner disc that depends on the black hole spin and lamppost height. For a fixed $h$, the ionisation parameter is also expected to increase as ${\lambda }^3$, where $\lambda$ is the observed bolometric Eddington ratio of the AGN. Comparing this formula to the observed $\xi$-$\lambda$ relationship for Mrk 335 yields $h\propto {\lambda }^{0.5-0.6}$, supporting the view of a dynamic X-ray corona in AGNs.

5 pages, 5 figures, accepted by MNRAS Letters

References in corpus (6)

• Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei
• Broad iron K-alpha emission lines as a diagnostic of black hole spin
• Conservative GRMHD Simulations of Moderately Thin, Tilted Accretion Disks
• Simultaneous spectral and reverberation modelling of relativistic reflection in Mrk 335
• AGN Coronae Through A Jet Perspective
• Dependence of the broad Fe K$\alpha$ line on the physical parameters of AGN

Cited by in corpus (4)

• Evidence for an emerging disc wind and collimated outflow during an X-ray flare in the narrow-line Seyfert 1 galaxy Mrk 335
• reXcor: A Model of the X-ray Spectrum of Active Galactic Nuclei that Combines Ionized Reflection and a Warm Corona
• Sustaining a Warm Corona in Active Galactic Nuclei Accretion Discs
• Black Hole Spin Measurements Based on a Thin Disc Model with Finite Thickness I. An example study of MCG-06-30-15