A deep X-ray view of the bare AGN Ark 120. II. Evidence for Fe K emission transients

Abstract

We report on the results from a large observational campaign on the bare Seyfert galaxy Ark 120, jointly carried out in 2014 with XMM-Newton, Chandra, and NuSTAR. The fortunate line of sight to this source, devoid of any significant absorbing material, provides an incomparably clean view to the nuclear regions of an active galaxy. Here we focus on the analysis of the iron fluorescence features, which form a composite emission pattern in the 6$-$7 keV band. The prominent K$\alpha$ line from neutral iron at 6.4 keV is resolved in the Chandra High-Energy Transmission Grating spectrum to a full-width at half maximum of 4700${}_{-1500}^{+2700}$ km s${}^{-1}$, consistent with an origin from the optical broad-line region. Excess components are detected on both sides of the narrow K$\alpha$ line: the red one (6.0$-$6.3 keV) clearly varies in strength in about one year, and hints at the presence of a broad, mildly asymmetric line from the accretion disk; the blue one (6.5$-$7.0 keV), instead, is likely a blend of different contributions, and appears to be constant when integrated over long enough exposures. However, the Fe K excess emission map computed over the 7.5 days of the XMM-Newton monitoring shows that both the red and the blue features are actually highly variable on timescales of $\sim$10$-$15 hours, suggesting that they might arise from short-lived hotspots on the disk surface, located within a few tens of gravitational radii from the central supermassive black hole and possibly illuminated by magnetic reconnection events. Any alternative explanation would still require a highly dynamic, inhomogeneous disk/coronal system, involving clumpiness and/or instability.

arXiv comment25 pages, 10+2 figures, 5 tables. Accepted for publication in The Astrophysical Journal

References in corpus (62)

• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• Improved Reflection Models of Black-Hole Accretion Disks: Treating the Angular Distribution of X-rays
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei: I. Comparing the Photoionization and Reverberation Techniques
• Intrinsic disc emission and the Soft X-ray Excess in AGN
• The 70 Month Swift-BAT All-Sky Hard X-Ray Survey
• A light bending model for the X-ray temporal and spectral properties of accreting black holes
• How many cosmological parameters?
• Non-linear X-ray variability in X-ray binaries and active galaxies
• Relativistic X-ray Lines from the Inner Accretion Disks Around Black Holes
• Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes
• The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight
• A Model for the X-Ray and UV Emission from Seyfert Galaxies and Galactic Black Holes
• Photoionization Modeling and the K Lines of Iron
• Broad emission lines for negatively spinning black holes
• Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from the Hubble Space Telescope
• Suzaku observations of 'bare' active galactic nuclei
• A rapidly spinning supermassive black hole at the centre of NGC 1365
• An extended scheme for fitting X-ray data with accretion disk spectra in the strong gravity regime
• Understanding X-ray reflection emissivity profiles in AGN: Locating the X-ray source
• Spectral evolution of magnetic flares and time lags in accreting black hole sources
• Normalizing a Relativistic Model of X-ray Reflection: The Definition of the Reflection Fraction and its Implementation in relxill
• The Cores of the Fe K$\alpha$ Lines in Active Galactic Nuclei: an Extended Chandra High Energy Grating Sample
• Variable partial covering and a relativistic iron line in NGC 1365
• Accretion disc coronae as magnetic reservoirs
• On the Iwasawa-Taniguchi effect of radio-quiet AGN
• Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?
• Photon Bubbles in Accretion Discs
• The Structure of the X-ray and Optical Emitting Regions of the Lensed Quasar Q 2237+0305
• General relativistic modelling of the negative reverberation X-ray time delays in AGN
• Cross-calibration of the X-ray Instruments onboard the Chandra, INTEGRAL, RXTE, Suzaku, Swift, and XMM-Newton Observatories using G21.5-0.9
• The variability of accretion onto Schwarzschild black holes from turbulent magnetized discs
• Flux and energy modulation of redshifted iron emission in NGC3516: implications for the black hole mass
• The broad band spectral variability of MCG-6-30-15 observed by NuSTAR and XMM-Newton
• Local Radiative Hydrodynamic and Magnetohydrodynamic Instabilities in Optically Thick Media
• Super-Eddington Atmospheres that Don't Blow Away
• The Comptonisation of accretion disc X-ray emission: Consequences for X-ray reflection and the geometry of AGN coronae
• The soft X-ray emission of Ark 120. XMM-Newton, NuSTAR, and the importance of taking the broad view
• Iron and Nickel properties in the X-ray reflecting region of the Circinus Galaxy
• Iron line profiles in Suzaku spectra of bare Seyfert galaxies
• Relativistic spectral features from X-ray illuminated spots and the measure of the black hole mass in AGN
• A Revised Calibration of the Virial Mass Estimator for Black Holes in Active Galaxies Based on Single-epoch H$\beta$ Spectra
• An XMM-Newton observation of Ark 120: the X-ray spectrum of a `bare' Seyfert 1 nucleus
• A reflection origin for the soft and hard X-ray excess of Ark 120
• XMM-Newton observation of the Seyfert 1.8 ESO 113-G010: discovery of a highly redshifted iron line at 5.4 keV
• 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
• On the lamppost model of accreting black holes
• On the evidence for narrow, relativistically shifted X-ray lines
• Discovery of a relativistic Fe line in PG 1425+267 with XMM--Newton and study of its short-timescale variability
• The Compton shoulder of the Fe Kalpha fluorescent emission line in active galactic nuclei
• Narrow Moving Fe K-alpha lines from magnetic flares in AGN
• Unveiling the broad band X-ray continuum and iron line complex in Mkr 841
• Probing variability patterns of the Fe K line complex in bright nearby AGNs
• A deep X-ray view of the bare AGN Ark 120. I. Revealing the Soft X-ray Line Emission
• The hard X-ray perspective on the soft X-ray excess
• X-ray Reflection from Inhomogeneous Accretion Disks: I. Toy Models and Photon Bubbles
• The hard X-ray spectrum of NGC 1365: scattered light, not black hole spin
• Iron lines from transient and persisting hot spots on AGN accretion disks
• Correlated modulation between the redshifted Fe K alpha line and the continuum emission in NGC 3783
• Investigating the reflection contribution to the X-ray emission of Ton S180
• X-ray Reflection from Inhomogeneous Accretion Disks: II. Emission Line Variability and Implications for Reverberation Mapping

Cited by in corpus (24)

• Towards precision measurements of accreting black holes using X-ray reflection spectroscopy
• High Density Reflection Spectroscopy: II. the Density of the Inner Black Hole Accretion Disc in AGN
• A deep X-ray view of the bare AGN Ark120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes
• The Soft-Excess in Mrk 509: Warm Corona or Relativistic Reflection?
• A Possible ~20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-Quiet Active Galactic Nucleus Ark 120
• A deep X-ray view of the bare AGN Ark120. V. Spin determination from disc-Comptonisation efficiency method
• The Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy
• Tracking the Iron K$\alpha$ line and the Ultra Fast Outflow in NGC 2992 at different accretion states
• The first broadband X-ray view of the narrow line Seyfert 1 Ton S180
• A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability
• X-ray, UV and optical time delays in the bright Seyfert galaxy Ark 120 with co-ordinated Swift and ground-based observations
• The lively accretion disk in NGC 2992. I. Transient iron K emission lines in the high flux state
• Long term X-Ray Observations of Seyfert 1 Galaxy Ark 120: On the origin of soft-excess
• Correlation between relativistic reflection fraction and photon index in NuSTAR sample of Seyfert 1 AGN
• A deep X-ray view of the bare AGN Ark 120. VI. Geometry of the hot corona from spectroscopic and polarization signatures
• Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120
• Towards an informed quest for accretion disc winds in quasars: the intriguing case of Ton 28
• Direct observation of the Broad Line Region in X-rays during the low state of NGC4051
• Short time-scale X-ray spectral variability in the Seyfert 1 galaxy NGC 3783
• Origins of the UV/X-ray Relation in Arakelian 120
• The Low Temperature Corona in ESO 511$-$G030 Revealed by NuSTAR and XMM-Newton
• Hard X-Ray broadband spectroscopy of Mrk 876: characterizing its spectrum
• The Profiles of Fe Kα Line From the Inhomogeneous Accretion Flow
• Poynting-Robertson effect on black-hole-driven winds