Revealing the X-ray Variability of AGN with Principal Component Analysis

Abstract

We analyse a sample of 26 active galactic nuclei with deep XMM-Newton observations, using principal component analysis (PCA) to find model independent spectra of the different variable components. In total, we identify at least 12 qualitatively different patterns of spectral variability, involving several different mechanisms, including five sources which show evidence of variable relativistic reflection (MCG-6-30-15, NGC 4051, 1H 0707-495, NGC 3516 and Mrk 766) and three which show evidence of varying partial covering neutral absorption (NGC 4395, NGC 1365, and NGC 4151). In over half of the sources studied, the variability is dominated by changes in a power law continuum, both in terms of changes in flux and power law index, which could be produced by propagating fluctuations within the corona. Simulations are used to find unique predictions for different physical models, and we then attempt to qualitatively match the results from the simulations to the behaviour observed in the real data. We are able to explain a large proportion of the variability in these sources using simple models of spectral variability, but more complex models may be needed for the remainder. We have begun the process of building up a library of different principal components, so that spectral variability in AGN can quickly be matched to physical processes. We show that PCA can be an extremely powerful tool for distinguishing different patterns of variability in AGN, and that it can be used effectively on the large amounts of high-quality archival data available from the current generation of X-ray telescopes.

arXiv comment25 pages, 27 figures, accepted to MNRAS. Analysis code available on request to lead author. Edit: Rogue table removed

References in corpus (75)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• Intrinsic disc emission and the Soft X-ray Excess in AGN
• A light bending model for the X-ray temporal and spectral properties of accreting black holes
• X-ray reflected spectra from accretion disk models. III. A complete grid of ionized reflection calculations
• Measuring Black Hole Spin using X-ray Reflection Spectroscopy
• X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180
• Suzaku observations of 'bare' active galactic nuclei
• A rapidly spinning supermassive black hole at the centre of NGC 1365
• Discovery of a relation between black hole mass and soft X-ray time lags in active galactic nuclei
• Broad iron L-line and X-ray reverberation in 1H0707-495
• The lack of variability of the iron line in MCG-6-30-15: general relativistic effects
• Complex resonance absorption structure in the X-ray spectrum of IRAS13349+2438
• A long, hard look at MCG-6-30-15 with XMM-Newton II: detailed EPIC analysis and modelling
• On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
• An absorption origin for the X-ray spectral variability of MCG-6-30-15
• Relativistic iron K X-ray Reverberation in NGC 4151
• XMM-Newton study of the complex and variable spectrum of NGC 4051
• X-ray Absorption and Reflection in Active Galactic Nuclei
• NuSTAR Spectroscopy of GRS 1915+105: Disk Reflection, Spin, and Connections to Jets
• The Reflection Component from Cygnus X-1 in the Soft State Measured by NuSTAR and Suzaku
• The NuSTAR spectrum of Mrk 335: Extreme relativistic effects within 2 gravitational radii of the event horizon?
• Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?
• 1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon
• Modelling the broad Fe Kα reverberation in the AGN NGC 4151
• The 2-79 keV X-ray Spectrum of the Circinus Galaxy with NuSTAR, XMM-Newton and Chandra: a Fully Compton-Thick AGN
• XMM-Newton discovery of a sharp spectral feature at ~7 keV in the Narrow-Line Seyfert 1 galaxy 1H 0707-495
• Negative X-ray reverberation time delays from MCG-6-30-15 and Mrk 766
• The variable X-ray spectrum of Markarian 766 - I. Principal components analysis
• 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
• RE J1034+396: The origin of the soft X-ray excess and QPO
• The Closest Look at 1H0707-495: X-ray Reverberation Lags with 1.3 Ms of Data
• NuSTAR and XMM-Newton Observations of NGC 1365: Extreme Absorption Variability and a Constant Inner Accretion Disk
• The nature of X-ray spectral variability in Seyfert Galaxies
• Iron K$\alpha$ emission in type-I and type-II Active Galactic Nuclei
• Effects of Kerr Spacetime on Spectral Features from X-Ray Illuminated Accretion Discs
• Revealing the X-ray source in IRAS 13224-3809 through flux-dependent reverberation lags
• Constraints on the Neutron Star and Inner Accretion Flow in Serpens X-1 Using NuSTAR
• X-ray reflection in the Seyfert galaxy 1H0419-577 revealing strong relativistic effects in the vicinity of a Kerr black hole
• The soft X-ray emission of Ark 120. XMM-Newton, NuSTAR, and the importance of taking the broad view
• XMM-Newton observations of the Narrow-Line Seyfert 1 galaxy Mrk 335 in an historical low X-ray flux state
• The variable OVIII Warm Absorber in MCG-6-30-15
• The Variable X-ray Spectrum of Markarian 766 - II. Time-Resolved Spectroscopy
• XMM-Newton spectral properties of the Narrow-Line Seyfert 1 galaxy IRAS 13224--3809
• A reflection origin for the soft and hard X-ray excess of Ark 120
• A blurred reflection interpretation for the intermediate flux state in Mrk 335
• PG 1211+143: probing high frequency lags in a high mass AGN
• Detection of a QPO in 5 XMM-Newton observations of RE J1034+396
• Bimodal spectral variability of Cygnus X-1 in an intermediate state
• Relativistic O VIII Emission and Ionized Outflow in NGC 4051
• Suzaku Observation of a Hard Excess in 1H 0419-577: Detection of a Compton-Thick Partial-Covering Absorber
• The curious time lags of PG 1244+026: Discovery of the iron K reverberation lag
• The Connection between Ultraviolet and X-ray Outflows in AGN: the case of PDS 456
• The flux-dependent X-ray time lags in NGC 4051
• Resolving the large scale spectral variability of the luminous Seyfert 1 galaxy 1H 0419-577: Evidence for a new emission component and absorption by cold dense matter
• PDS 456: an Extreme Accretion Rate Quasar?
• X-ray Characteristics of NGC 3516: A View through the Complex Absorber
• The effects of X-ray absorption variability in NGC 4395
• Variability of the High Velocity Outflow in the Quasar PDS 456
• Constraints on the absorption-dominated model for the X-ray spectrum of MCG-6-30-15
• An XMM-Newton observation of the Seyfert 1 galaxy 1H 0419-577 in an extreme low state
• Principal Component Analysis of MCG--6-30-15 with XMM-Newton
• 2006 May-July Major Radio Flare episodes in Cygnus X-3: spectro-timing analysis of the X-ray data
• Suzaku Studies of the Central Engine in the Typical Type I Seyfert NGC 3227: Detection of Multiple Primary X-ray Continua with Distinct Properties
• Remarkable Spectral Variability of PDS 456
• The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines
• The warm absorber and X-ray variability of the Seyfert 1 galaxy NGC 3516 as seen by the XMM-Newton RGS
• The variable XMM-Newton spectrum of Markarian 766
• The NeXT Mission
• PCA of PCA: Principal Component Analysis of Partial Covering Absorption in NGC 1365
• Multiwavelength campaign on Mrk 509: Reverberation of the Fe Kalpha line
• Suzaku Discovery of a Slowly Varying Hard X-ray Continuum from the Type I Seyfert Galaxy NGC 3516

Cited by in corpus (43)

• A global look at X-ray time lags in Seyfert Galaxies
• A dynamic black hole corona in an active galaxy through X-ray reverberation mapping
• Accretion disks and coronae in the X-ray flashlight
• Discovery of a ~2 hr high frequency X-ray QPO and iron K alpha reverberation in the active galaxy MS 2254.9-3712
• Revealing the ultra-fast outflow in IRAS 13224-3809 through spectral variability
• Broad Hbeta Emission-Line Variability in a Sample of 102 Local Active Galaxies
• Revisiting The Spectral and Timing Properties of NGC 4151
• Revealing structure and evolution within the corona of the Seyfert galaxy I Zw 1
• Lyman continuum leaking AGN in the SSA22 field
• Tracking the Iron K$\alpha$ line and the Ultra Fast Outflow in NGC 2992 at different accretion states
• Using principal component analysis to understand the variability of PDS 456
• A high-density relativistic reflection origin for the soft and hard X-ray excess emission from Mrk 1044
• A Relativistic Disc Reflection Model for 1H0419-577: Multi-Epoch Spectral Analysis with XMM-Newton and NuSTAR
• The nature of the extreme X-ray variability in the NLS1 1H 0707-495
• Probing the effects of a thermonuclear X-ray burst on the neutron star accretion flow with NuSTAR
• The eROSITA Final Equatorial Depth Survey (eFEDS): Complex absorption and soft excesses in hard X-ray--selected active galactic nuclei
• Highly variable AGN from the XMM-Newton Slew Survey
• NuSTAR observations of Mrk 766: distinguishing reflection from absorption
• Constraining the X-ray reflection in low accretion rate AGN using XMM-Newton, NuSTAR and Swift
• A statistical study of the optical spectral variability in gamma-ray blazars
• X-ray flaring in PDS 456 observed in a high-flux state
• The nature of the soft-excess and spectral variability in the Seyfert 1 galaxy Zw 229.015
• The X-ray variability of Seyfert 1.8/1.9 galaxies
• Multi-epoch X-ray spectral analysis of the narrow-line Seyfert 1 galaxy Mrk 478
• Ejection-accretion connection in NLS1 AGN 1H 1934-063
• X-ray spectral variability of blazars using principal component analysis
• Quasi periodic oscillations in active galactic nuclei
• Evidence of spreading layer emission in thermonuclear superbursts
• The nature of the broadband X-ray variability in the dwarf Seyfert galaxy NGC 4395
• Variable blurred reflection in the narrow-line Seyfert 1 galaxy Mrk 493
• AGN X-ray Spectroscopy with Neural Networks
• The nature of X-ray spectral variability in MCG-6-30-15
• X-ray Variability in the Symbiotic Binary RT Cru: Principal Component Analysis
• Modelling X-ray RMS spectra II: the ultra-fast outflow of PDS 456
• NuSTAR observations of a heavily X-ray obscured AGN in the dwarf galaxy J144013+024744
• X-ray Eclipses of Active Galactic Nuclei
• A Systematic Study of the Short-Term X-ray Variability of Seyfert Galaxies I. Diversity of the X-ray Rms Spectra
• Disentangling the X-ray variability in the Lyman continuum emitter Haro 11
• Relativistic Reflection Modeling in AGN and Related Variability from PCA: A Brief Review
• The broad band SEDs of four 'hypervariable' AGN
• Relativistic spectroscopy of the extreme NLS1 IRAS13224-3809
• IGR J12580+0134: The Nearest Tidal Disruption Event and its Faint Resurrection
• Accretion-disk reflection in the Seyfert 1 galaxy NGC 3783 as viewed by Chandra grating spectroscopy