Flare-induced fountains and buried flares in AGN

Abstract

We discuss the local physical changes at the surface of an AGN accretion disk after the onset of a magnetic flare. The X-ray irradiation by a flare creates a hot spot at the disk surface where the plasma both heats up and expands in the vertical direction in order to regain the hydrostatic equilibrium. Assuming that the magnetic loop causing the flare is anchored deeply within the disk interior, we derive analytical estimates for the vertical dimension H_hot and the optical depth tau_es of the heated atmosphere as a function of the position within the spot. We perform computations for various values of the accretion rate dm/dt, the fraction f_cor of radiation dissipated within the disk corona, and the covering factor f_cover of the disk surface with flare-illuminated patches. It turns out that generally we can distinguish three characteristic radial zones within the disk showing a qualitatively different behavior of the heated material. In the innermost regions of the disk (inner zone) the expansion of the disk material is restricted by strong gravitational forces. Further out, the flare source, initially above the disk, soon becomes embedded by the expanding disk atmosphere. At these intermediate disk radii (middle zone) the material is optically thick thus greatly modifying the observed radiation by multiple Compton scattering. We show exemplary spectra models obtained from Monte Carlo simulations illustrating the trends. In the outermost regions of the disk (outer zone) the expanding material is optically thin and its influence on the observed spectra is smaller but pressure gradients in radial directions should cause the development of a fountain-like dynamical structure around the flare source. We discuss the observational consequences of our results.

arXiv comment12 pages, 14 figures, accepted by Astronomy & Astrophysics

References in corpus (39)

• Measuring the broadband power spectra of active galactic nuclei with RXTE
• The Formation and Structure of a Strongly Magnetized Corona above Weakly Magnetized Accretion Disks
• Plasma Ejection from Magnetic Flares and the X-ray Spectrum of Cygnus X-1
• A Model for the X-Ray and UV Emission from Seyfert Galaxies and Galactic Black Holes
• X-ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies
• Thermal Instability and Photoionized X-ray Reflection in Accretion Disks
• Spectral evolution of magnetic flares and time lags in accreting black hole sources
• Coronal outflow dominated accretion discs: a new possibility for low luminosity black holes?
• X-ray Reflection By Photoionized Accretion Discs
• Magnetic reconnection: flares and coronal heating in Active Galactic Nuclei
• Hot Disk Corona and Magnetic Turbulence in Radio-Quiet Active Galactic Nuclei: Observational Constraints
• Universal spectral shape of high accretion rate AGN
• On the Vertical Structure of Radiation-Dominated Accretion Disks
• A simple model for magnetic reconnection heated corona
• The Fragmentation of Pre-enriched Primordial Objects
• Far UV Spectra of Fast Coronal Mass Ejections Associated with X-class Flares
• Evidence for Rapid Iron K_alpha Line Flux Variability in MCG--6-30-15
• Application of a relativistic accretion disc model to X-ray spectra of LMC X-1 and GRO J1655-40
• Magnetic flares in accretion disc coronae and the Spectral States of black hole candidates: the case of GX 339-4
• Beyond the standard accretion disc model: coupled magnetic disc--corona solutions with a physically motivated viscosity law
• The structure and radiation spectra of illuminated accretion discs in AGN. I. Moderate illumination
• Black hole masses from power density spectra: determinations and consequences
• The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s
• Vertical Structure of Accretion Discs with Hot Coronae in AGN
• The shape of the relativistic iron K-alpha line from MCG6--6-30-15 measured with the Chandra HETGS and RXTE
• Effects of non-thermal tails in Maxwellian electron distributions on synchrotron and Compton processes
• The structure and radiation spectra of illuminated accretion disks in AGN. II. Flare/spot model of X-ray variability
• Evolution of the X-ray spectrum in the flare model of Active Galactic Nuclei
• An XMM-Newton observation of Ton S180: Constraints on the continuum emission in ultrasoft Seyfert galaxies
• The intrinsic emission of Seyfert galaxies observed with BeppoSAX/PDS I. Comparison of the average spectra of the three classes of Seyfert Galaxies
• On time-dependent X-ray reflection by photoionized accretion disks: implication for Fe K-alpha line reverberation studies of AGN
• Narrow Moving Fe K-alpha lines from magnetic flares in AGN
• A Complete Relativistic Ionized Accretion Disc in Cygnus X-1
• The effects of relativistic bulk motion of X-ray flares in the corona on the iron Kalpha line in Seyfert 1 galaxies
• On the accretion geometry of Cyg X-1 in the low/hard state
• Predictions for Fourier-resolved X-ray spectroscopy from the model of magnetic flare avalanches above an accretion disc with hot ionized skin
• Testing models of X-ray reflection from irradiated disks
• Testing the X-ray variability of active galactic nuclei with the nonlinear prediction method
• Testing a model of variability of X-ray reprocessing features in Active Galactic Nuclei

Cited by in corpus (9)

• Can the soft excess in AGN originate from disc reflection?
• The role of absorption and reflection in the soft X-ray excess of Active Galactic Nuclei : 1. Preliminary results
• Origin of the X-ray disc-reflection steep radial emissivity
• Iron lines from transient and persisting hot spots on AGN accretion disks
• Light Echoes in Kerr Geometry: A Source of High Frequency QPOs from Random X-ray Bursts
• What shapes the Absorption Measure Distribution in AGN outflows
• Anisotropic X-ray emission in AGN accretion discs
• Modeling time delays in the X-ray spectrum of the Seyfert galaxy MCG-6-30-15
• Line shifts in accretion disks - the case of Fe K$\alpha$