Ultraviolet and X-ray variability of active galactic nuclei with Swift

Abstract

We analyse a sample of 21 active galactic nuclei (AGN) using data from the Swift satellite to study the variability properties of the population in the X-ray, UV and optical band. We find that the variable part of the UV-optical emission has a spectrum consistent with a powerlaw, with an average index of $-2.21\pm 0.13$, as would be expected from central illumination of a thin disc (index of -7/3). We also calculate the slope of a powerlaw from UV to X-ray variable emission, ${\alpha }_{\mathrm{OX},\mathrm{Var}}$; the average for this sample is ${\alpha }_{\mathrm{OX},\mathrm{Var}}=-1.06\pm 0.04$. The anticorrelation of ${\alpha }_{\mathrm{OX}}$ with the UV luminosity, $L_{\mathrm{UV}}$, previously found in the average emission is also present in the variable part: ${\alpha }_{\mathrm{OX},\mathrm{Var}}=(-0.177\pm 0.083)\log (L_{\nu ,\mathrm{Var}}(2500\mathring{A}))+(3.88\pm 2.33)$. Correlated variability between the emission in X-rays and UV is detected significantly for 9 of the 21 sources. All these cases are consistent with the UV lagging the X-rays, as would be seen if the correlated UV variations were produced by the reprocessing of X-ray emission. The observed UV lags are tentatively longer than expected for a standard thin disc.

arXiv comment14 pages, 8 figures, 4 tables in main text, plus 15 pages of figures in appendices. Accepted for publication in MNRAS

References in corpus (105)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The Swift X-ray Telescope
• The Swift Ultra-Violet/Optical Telescope
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• Composite Quasar Spectra From the Sloan Digital Sky Survey
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• On characterising the variability properties of X-ray light curves from active galaxies
• Photometric Calibration of the Swift Ultraviolet/Optical Telescope
• An online repository of Swift/XRT light curves of GRBs
• On Uncertainties in Cross-Correlation Lags and the Reality of Wavelength-Dependent Continuum Lags in Active Galactic Nuclei
• The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements II. The Full Sample of Reverberation-Mapped AGNs
• The Rest-Frame Extreme Ultraviolet Spectral Properties of QSOs
• The X-ray-to-Optical Properties of Optically-Selected Active Galaxies Over Wide Luminosity and Redshift Ranges
• A light bending model for the X-ray temporal and spectral properties of accreting black holes
• Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei
• X-ray reverberation around accreting black holes
• Non-linear X-ray variability in X-ray binaries and active galaxies
• X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180
• Determining Central Black Hole Masses in Distant Active Galaxies
• The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey
• The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements
• Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample
• The Quasar Accretion Disk Size -- Black Hole Mass Relation
• The Quasar Accretion Disk Size - Black Hole Mass Relation
• The AGN Black Hole Mass Database
• Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Testing thermal reprocessing in AGN accretion discs
• The Hard X-ray Spectrum as a Probe for Black-Hole Growth in Radio-Quiet Active Galactic Nuclei
• The Simultaneous Optical-to-X-ray Spectral Energy Distribution of Soft X-ray Selected AGN observed by Swift
• X-ray emission from radio-quiet quasars in the SDSS Early Data Release. The alpha_ox dependence upon UV luminosity
• CAIXA: a Catalogue of AGN In the XMM-Newton Archive I. Spectral analysis
• Soft X-ray and Ultraviolet Emission Relations in Optically Selected AGN Samples
• Broad iron L-line and X-ray reverberation in 1H0707-495
• The tight relation between X-ray and ultraviolet luminosity of quasars
• X-ray variability of 104 active galactic nuclei. XMM-Newton power-spectrum density profiles
• X-Ray and Optical Variability in NGC 4051 and the Nature of Narrow-Line Seyfert 1 Galaxies
• On the Reliability of Cross Correlation Function Lag Determinations in Active Galactic Nuclei
• Quasar Accretion Disks Are Strongly Inhomogeneous
• The iron line in MCG-6-30-15 from XMM-Newton: evidence for gravitational light-bending?
• An absorption origin for the X-ray spectral variability of MCG-6-30-15
• Mapping the radial structure of AGN tori
• The Variable Diffuse Continuum Emission of Broad Line Clouds
• Multiwavelength campaign on Mrk 509. IV. Optical-UV-X-ray variability and the nature of the soft X-ray excess
• HST-COS Observations of AGN. I. Ultraviolet Composite Spectra of the Ionizing Continuum and Emission Lines
• A Stochastic Model for the Luminosity Fluctuations of Accreting Black Holes
• Variability in black hole accretion discs
• Correlated long-term optical and X-ray variations in NGC 5548
• The power output of local obscured and unobscured AGN: crossing the absorption barrier with Swift/BAT and IRAS
• The NuSTAR spectrum of Mrk 335: Extreme relativistic effects within 2 gravitational radii of the event horizon?
• 1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon
• Discovery of high-frequency iron K lags in Ark 564 and Mrk 335
• Are Optically-Selected Quasars Universally X-Ray Luminous? X-Ray/UV Relations in Sloan Digital Sky Survey Quasars
• A new direct method for measuring the Hubble constant from reverberating accretion discs in active galaxies
• The UV Continuum of Quasars: Models and SDSS Spectral Slopes
• New constraints on the continuum-emission mechanism of AGN: Intensive monitoring of NGC 7469 in the X-ray and ultraviolet
• Narrow Iron K$\alpha$ Lines in Active Galactic Nuclei: Evolving Populations?
• Spectral Analysis of 1H0707-495 with XMM-Newton
• The broad band spectral variability of MCG-6-30-15 observed by NuSTAR and XMM-Newton
• Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulation and spectral hardness on the superorbital phase
• The Closest Look at 1H0707-495: X-ray Reverberation Lags with 1.3 Ms of Data
• Revealing the X-ray source in IRAS 13224-3809 through flux-dependent reverberation lags
• Optical Spectral Properties of Swift BAT Hard X-ray Selected Active Galactic Nuclei Sources
• Twelve years of X-ray and optical variability in the Seyfert galaxy NGC 4051
• Gravitational Lensing Size Scales for Quasars
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• Multiwavelength Monitoring of the Narrow-Line Seyfert 1 Galaxy Akn 564. III. Optical Observations and the Optical--UV--X-ray Connection
• Detection of a possible X-ray Quasi-periodic Oscillation in the Active Galactic Nucleus 1H~0707-495
• The rapid X-ray variability of NGC 4051
• A remarkable long-term light curve, and deep, low-state spectroscopy: Swift & XMM-Newton monitoring of the NLS1 galaxy Mkn 335
• X-ray vs. Optical Variations in the Seyfert 1 Nucleus NGC 3516: A Puzzling Disconnectedness
• Correlated X-ray/Ultraviolet/Optical variability in the very low mass AGN NGC 4395
• Searching for Correlations in Simultaneous X-ray and UV Emission in the Narrow-line Seyfert 1 galaxy 1H 0707-495
• A High Signal-to-Noise UV Spectrum of NGC 7469: New Support for Reprocessing of Continuum Radiation
• Variability and the X-ray/UV ratio of active galactic nuclei. II. Analysis of a low-redshift Swift sample
• The Origin of UV-optical Variability in AGN and Test of Disc Models: XMM-Newton and ground based observations of NGC4395
• Variability of Active Galactic Nuclei from the Optical to X-ray Regions
• Long-term monitoring of the archetype Seyfert galaxy MCG-6-30-15: X-ray, optical and near-IR variability of the corona, disc and torus
• Variability and the X-ray/UV ratio of Active Galactic Nuclei
• Correlated X-ray/Ultraviolet/Optical Variability in NGC 6814
• Correlated X-ray and Optical Variability in Mkn 509
• X-ray and Optical Correlation of Type I Seyfert NGC 3516 Studied with Suzaku and Japanese Ground-Based Telescopes
• X-ray time delays in the Narrow Line Seyfert 1 galaxy PG 1244+026
• X-ray and optical variability of Seyfert 1 galaxies as observed with XMM-Newton
• CIV and CIII] reverberation mapping of the luminous quasar PG 1247+267
• The Compton hump and variable blue wing in the extreme low-flux NuSTAR observations of 1H0707-495
• A Possible 100-day X-ray-to-Optical Lag in the Variations of the Seyfert 1 Nucleus NGC 3516
• Short Timescale AGN X-ray Variability with EXOSAT: Black hole mass and Normalised Variability Amplitude
• X-ray to UV Variability Correlation in MCG-6-30-15
• Discovery of a faint optical jet in 3C 120
• Multiwavelength campaign on Mrk 509. XIII. Testing ionized-reflection models on Mrk 509
• The X-ray Power Spectral Density Function and Black Hole Mass Estimate for the Seyfert AGN IC 4329a
• The relation of optical/UV and X-ray emission in low-luminosity active galactic nuclei
• Ultraviolet and X-ray variability of NGC 4051 over 45 days with XMM-Newton and Swift
• The changing X-ray time lag in MCG-6-30-15
• Studying X-ray reprocessing and continuum variability in quasars: PG 1211+143
• X-ray timing analysis of the quasar PG 1211+143
• Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-infrared Emission Lines
• Energy-dependent variability from accretion flows
• XMM-Newton observations of the Seyfert 1 AGN H0557-385
• The fast UV variability of the active galactic nucleus in Fairall 9
• Modelling the variable broad-band optical/UV/X-ray spectrum of PG1211+143: Implications for the ionized outflow

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