The 450 days X-ray monitoring of the changing-look AGN 1ES 1927+654

Abstract

1ES 1927+654 is a nearby active galactic nucleus (AGN) which underwent a changing-look event in early 2018, developing prominent broad Balmer lines which were absent in previous observations. We have followed up this object in the X-rays with an ongoing campaign that started in May 2018, and that includes 265 NICER (for a total of 678ks) and 14 Swift/XRT (26ks) observations, as well as three simultaneous XMM-Newton/NuSTAR (158/169 ks) exposures. In the X-rays, 1ES 1927+654 shows a behaviour unlike any previously known AGN. The source is extremely variable both in spectral shape and flux, and does not show any correlation between X-ray and UV flux on timescales of hours or weeks/months. After the outburst the power-law component almost completely disappeared, and the source showed an extremely soft continuum dominated by a blackbody component. The temperature of the blackbody increases with the luminosity, going from $kT\sim 80$eV (for a 0.3--2keV luminosity of $L_{0.3-2}\sim 10^{41.5}\mathrm{erg}{\mathrm{s}}^{-1}$) to $\sim 200$eV (for $L_{0.3-2}\sim 10^{44}\mathrm{erg}{\mathrm{s}}^{-1}$). The spectra show evidence of ionized outflows, and of a prominent feature at $\sim 1$keV, which can be reproduced by a broad emission line. The unique characteristics of 1ES 1927+654 in the X-ray band suggest that it belongs to a new type of changing-look AGN. Future X-ray surveys might detect several more objects with similar properties.

arXiv commentAccepted for publication in ApJS, 56 pages. The complete 114-pages manuscript will be available upon publication

References in corpus (170)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies
• The Demography of Massive Dark Objects in Galaxy Centres
• On the Absorption of X-rays in the Interstellar Medium
• 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 European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• The Swift Ultra-Violet/Optical Telescope
• Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• Hot Accretion Flows Around Black Holes
• ATLAS: A High-Cadence All-Sky Survey System
• On characterising the variability properties of X-ray light curves from active galaxies
• Nuclear Activity in Nearby Galaxies
• Revisiting the Unified Model of Active Galactic Nuclei
• The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
• Black Holes, Galaxy Formation, and the M_BH-sigma Relation
• Broad-band gamma-ray and X-ray spectra of NGC 4151 and their implications for physical processes and geometry
• Improved Reflection Models of Black-Hole Accretion Disks: Treating the Angular Distribution of X-rays
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• The XMM-Newton Optical/UV Monitor Telescope
• Evidence for ultra-fast outflows in radio-quiet AGNs: I - detection and statistical incidence of Fe K-shell absorption lines
• Intrinsic disc emission and the Soft X-ray Excess in AGN
• The May 1989 outburst of the Soft X-ray Transient GS 2023+338 (V404 Cyg)
• What Drives the Growth of Black Holes?
• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• Broad iron lines in Active Galactic Nuclei
• X-ray reflected spectra from accretion disk models. III. A complete grid of ionized reflection calculations
• Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei
• An Explanation for the soft X-ray excess in AGN
• The XMM-Newton view of PG quasars I. X-ray continuum and absorption
• Obscured Active Galactic Nuclei
• Is the soft excess in AGN real?
• The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
• Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes
• Multiwavelength Observations of Strong Flares From the TeV-Blazar 1ES 1959+650
• Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample
• X-ray reflected spectra from accretion disk models. I. Constant density atmospheres
• Broad emission lines for negatively spinning black holes
• BAT AGN Spectroscopic Survey I: Spectral Measurements, Derived Quantities, and AGN Demographics
• The Formation and Evolution of Massive Black Holes
• Suzaku observations of 'bare' active galactic nuclei
• Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus
• Calibration of the NuSTAR High Energy Focusing X-ray Telescope
• X-ray Spectral Properties of the BAT AGN Sample
• Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
• The Fermi blazars divide
• A fast and long-lived outflow from the supermassive black hole in NGC 5548
• A global look at X-ray time lags in Seyfert Galaxies
• Explaining changing-look AGN with state transition triggered by rapid mass accretion rate drop
• First X-ray-Based Statistical Tests for Clumpy-Torus Models: Eclipse Events from 230 Years of Monitoring of Seyfert AGN
• The Hard X-ray Spectral Slope as an Accretion-Rate Indicator in Radio-Quiet Active Galactic Nuclei
• On the use of C-stat in testing models for X-ray spectra
• Broad Emission Line Regions in AGN: the Link with the Accretion Power
• Optical Variability in Active Galactic Nuclei: Starbursts or Disk Instabilities?
• Discovery of 21 New Changing-look AGNs in Northern Sky
• A statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys
• On the Disappearance of the Broad-Line Region in Low-Luminosity Agns
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• PS16dtm: A Tidal Disruption Event in a Narrow-line Seyfert 1 Galaxy
• 1ES 1927+654: An AGN Caught Changing Look on a Timescale of Months
• X-ray quasi-periodic eruptions from the galactic nucleus of RX J1301.9+2747
• Hidden Broad Line Seyfert 2 Galaxies in the CfA and 12micron Samples
• Unabsorbed Seyfert 2 galaxies
• Evolution of Broad-line Emission from Active Galactic Nuclei
• A Mid-IR Selected Changing-Look Quasar and Physical Scenarios for Abrupt AGN Fading
• A tidal disruption flare in a massive galaxy? Implications for the fuelling mechanisms of nuclear black holes
• The Cores of the Fe K$\alpha$ Lines in Active Galactic Nuclei: an Extended Chandra High Energy Grating Sample
• X-ray reflection in the NLS1 1H 0707-495
• Changing-Look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars
• The destruction and recreation of the X-ray corona in a changing-look Active Galactic Nucleus
• Swift monitoring of NGC 5548: X-ray reprocessing and short term UV/optical variability
• The long term X-ray spectral variability of AGN
• The Unified Model & Evolution of Active Galaxies: Implications from a Spectropolarimetric Study
• Towards an Understanding of Changing-Look Quasars: An Archival Spectroscopic Search in SDSS
• "Comets" orbiting a black hole
• BAT AGN Spectroscopic Survey -- XII. The relation between coronal properties of Active Galactic Nuclei and the Eddington ratio
• Seyfert galaxies in the local Universe (z$\le$ 0.1): the average X-ray spectrum as seen by $BeppoSAX$
• Accretion disc coronae as magnetic reservoirs
• On the Iwasawa-Taniguchi effect of radio-quiet AGN
• The hard X-ray spectral evolution in X-ray binaries and its application to constrain the black hole mass of ultraluminous X-ray sources
• The anti-correlation between the hard X-ray photon index and the Eddington ratio in LLAGNs
• NuSTAR catches the unveiling nucleus of NGC 1068
• Type 1 low z AGN. I. Emission properties
• The Close AGN Reference Survey (CARS) - Mrk 1018 returns to the shadows after 30 years as a Seyfert 1
• The Swift/BAT AGN Spectroscopic Survey (BASS) -- VI. The Gamma_X - L/L_Edd relation
• A new physical interpretation of optical and infrared variability in quasars
• Properties of AGN coronae in the NuSTAR era II: hybrid plasma
• Long XMM observation of the Narrow-Line Seyfert 1 galaxy IRAS13224-3809: rapid variability, high spin and a soft lag
• AGN Obscuration and the Unified Model
• The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black Holes: New Insights from Faded Changing-Look Quasars
• Quasar Viscosity Crisis
• A NuSTAR census of coronal parameters in Seyfert galaxies
• GSN 069 -- A Tidal Disruption Near-Miss
• The XMM-Newton long look of NGC 1365: uncovering of the obscured X-ray source
• A New Class of Changing-Look LINERs
• Black-Hole Mass and Growth Rate at z~4.8: A Short Episode of Fast Growth Followed by Short Duty Cycle Activity
• A new class of flares from accreting supermassive black holes
• RBSC-NVSS Sample. I. Radio and Optical Identifications of a Complete Sample of 1500 Bright X-ray Sources
• The Link Between the Hidden Broad Line Region and the Accretion Rate in Seyfert 2 Galaxies
• A likely decade-long sustained tidal disruption event
• X-Ray/Ultraviolet Observing Campaign of the Markarian 279 Active Galactic Nucleus Outflow: a close look at the absorbing/emitting gas with Chandra-LETGS
• Reflection in Seyfert Galaxies and the Unified Model of AGN
• The Soft-Excess in Mrk 509: Warm Corona or Relativistic Reflection?
• Iron K$\alpha$ emission in type-I and type-II Active Galactic Nuclei
• Tidal disruption events in active galactic nuclei
• Probing the Balance of AGN and Star-Forming Activity in the Local Universe with ChaMP
• The high-Eddington NLS1 Ark 564 has the coolest corona
• Study of LINER sources with broad H(alpha) emission. X-ray properties and comparision to luminous AGN and X-ray binaries
• IC 751: a new changing-look AGN discovered by NuSTAR
• New changing look case in NGC 1566
• X-ray spectral and eclipsing model of the clumpy obscurer in active galactic nuclei
• An Iron K Component to the Ultrafast Outflow in NGC 1313 X-1
• Unobscured Type 2 AGNs
• A hard X-ray view of the soft excess in AGN
• The Close AGN Reference Survey (CARS) - What is causing Mrk1018's return to the shadows after 30 years?
• XMM-Newton spectral properties of the Narrow-Line Seyfert 1 galaxy IRAS 13224--3809
• A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies
• Long-term spectral changes in the partial-covering candidate NLS1 1H 0707-495
• A high Eddington-ratio, true Seyfert 2 galaxy candidate: implications for broad-line-region models
• A long decay of X-ray flux and spectral evolution in the supersoft active galactic nucleus GSN 069
• Indecent Exposure in Seyfert 2 Galaxies: A Close Look
• The detection and X-ray view of the changing look AGN HE 1136-2304
• The hard X-ray spectrum of NGC 5506 as seen by NuSTAR
• Energy-dependent variability and the origin of the soft X-ray excess in AGN
• Long-term X-Ray Spectral Variability in AGN from the Palomar sample observed by Swift
• Accretion Disk Temperatures and Continuum Colors in QSOs
• NuSTAR Survey of Obscured Swift/BAT-selected Active Galactic Nuclei: II. Median High-energy Cutoff in Seyfert II Hard X-ray Spectra
• An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. I. Evidence for a shocked outflow
• On the nature of unabsorbed Seyfert 2 galaxies
• Modelling the Extreme X-ray Spectrum of IRAS 13224-3809
• The `harder when brighter' X-ray behaviour of the low luminosity active galactic nucleus NGC 7213
• Initial results from a systematic search for changing-look active galactic nuclei selected via mid-infrared variability
• RX J1301.9+2747: A Highly Variable Seyfert Galaxy with Extremely Soft X-ray Emission
• Simultaneous X-ray and optical observations of true Type 2 Seyfert galaxies
• A model for AGN variability on multiple timescales
• A close look at the state transitions of Galactic black hole transients during outburst decay
• Luminosity-dependent unification of Active Galactic Nuclei and the X-ray Baldwin effect
• Rapid "Turn-on" of type 1 AGN in a quiescent early type galaxy SDSS1115+0544
• Discovery of A Mg II Changing-look AGN and its Implications for a Unification Sequence of Changing-look AGNs
• Disk Outflows and High-Luminosity True Type 2 AGN
• A Candidate Active Galactic Nucleus with a Pure Soft Thermal X-ray Spectrum
• HST unveils a compact mildly relativistic Broad Line Region in the candidate true type 2 NGC 3147
• The Sloan Digital Sky Survey Reverberation Mapping Project: Accretion and Broad Emission Line Physics from a Hypervariable Quasar
• The Low-mass, Highly Accreting Black Hole Associated with the Active Galactic Nucleus 2XMM J123103.2+110648
• Unabsorbed Seyfert 2 galaxies: the case of "naked" AGN
• Upholding the Unified Model for Active Galactic Nuclei: VLT/FORS2 Spectropolarimetry of Seyfert 2 galaxies
• The frequency of extreme X-ray variability of radio-quiet quasars
• Broadband X-ray spectral analysis of the Seyfert 1 galaxy GRS 1734-292
• A Tidal Disruption Event Candidate Discovered in the Active Galactic Nucleus SDSS J022700.77-042020.6
• Large Decay of X-ray Flux in 2XMM J123103.2+110648: Evidence for a Tidal Disruption Event
• Accretion Disk Spectra of the Brightest Ultra-luminous X-ray Source in M82
• Obscuration in the Host Galaxies of Soft X-ray Selected Seyferts
• Coronal properties of Swift/BAT-selected Seyfert 1 AGN observed with NuSTAR
• A Low-Flux State in IRAS 00521-7054 seen with NuSTAR and XMM-Newton: Relativistic Reflection and an Ultrafast Outflow
• High-redshift Extreme Variability Quasars from Sloan Digital Sky Survey Multi-Epoch Spectroscopy
• 1ES 1927+654: Persistent and rapid X-ray variability in an AGN with low intrinsic neutral X-ray absorption and narrow optical emission lines
• A stratified ultrafast outflow in 1H0707-495?
• Recurring obscuration in NGC 3783
• Central Engine and Host Galaxy of RXJ 1301.9+2747: A Multiwavelength View of a Low-mass Black Hole Active Galactic Nuclei with Ultra-soft X-ray Emission
• Relativistic components of the Ultra-Fast Outflow in the Quasar PDS 456 from Chandra/HETGS, NuSTAR and XMM-Newton observations
• The role of the Gamma-Eddington ratio relation on the X-ray Baldwin effect in Active Galactic Nuclei
• An Iwasawa-Taniguchi Effect for Compton-thick Active Galactic Nuclei
• The Close AGN Reference Survey (CARS): Mrk 1018 halts dimming and experiences strong short-term variability
• Light curves of tidal disruption events in active galactic nuclei
• 1ES 1927+654: a bare Seyfert 2
• A receding torus model for the Iwasawa-Taniguchi effect for Compton-thick AGN
• The NuSTAR view of the true Type 2 Seyfert NGC3147

Cited by in corpus (34)

• Science objectives of the Einstein Probe mission
• The Curious Case of ASASSN-20hx: A Slowly-Evolving, UV and X-ray Luminous, Ambiguous Nuclear Transient
• Comprehensive Broadband X-ray and Multiwavelength Study of Active Galactic Nuclei in Local 57 Ultra/luminous Infrared Galaxies Observed with NuSTAR and/or Swift/BAT
• The Host Galaxy and Rapidly Evolving Broad-line Region in the Changing-look Active Galactic Nucleus 1ES 1927+654
• The rebrightening of a ROSAT-selected tidal disruption event: repeated weak partial disruption flares from a quiescent galaxy?
• Evolution of a Relativistic Outflow and X-ray Corona in the Extreme Changing-Look AGN 1ES 1927+654
• BASS XXXIX: Swift-BAT AGN with changing-look optical spectra
• Broadband X-Ray Observations of the 2018 Outburst of the Changing-Look Active Galactic Nucleus NGC 1566
• Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko
• A Case for a Binary Black Hole System Revealed via Quasi-Periodic Outflows
• Discovery of the luminous X-ray ignition eRASSt J234402.9$-$352640; I. Tidal disruption event or a rapid increase in accretion in an active galactic nucleus?
• Investigating Changing-Look Active Galactic Nuclei with Long-term Optical and X-Ray Observations
• Improving the selection of changing-look AGNs through multi-wavelength photometric variability
• NuSTAR Observations of Intrinsically X-ray Weak Quasar Candidates: An Obscuration-Only Scenario
• The radio detection and accretion properties of the peculiar nuclear transient AT 2019avd
• Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy
• Local Active Galactic Nuclei with Large Broad-Hα Variability Reside in Red Galaxies
• Ejection-accretion connection in NLS1 AGN 1H 1934-063
• Multiple Flares in the Changing-Look AGN NGC 5273
• BASS-XL: X-ray variability properties of unobscured Active Galactic Nuclei
• Joint ALMA/X-ray monitoring of the radio-quiet type 1 AGN IC 4329A
• The lively accretion disk in NGC 2992. II. The 2019/2021 X-ray monitoring campaigns
• Transient radio emission from low-redshift galaxies at z<0.3 revealed by VLASS and FIRST surveys
• TESS Shines Light on the Origin of the Ambiguous Nuclear Transient ASASSN-18el
• A hard look at the X-ray spectral variability of NGC 7582
• Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum
• X-ray Unveiling Events in a z~1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
• A kinetic model of jet-corona coupling in accreting black holes
• AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system
• Intervening nuclear obscuration changing the X-ray look of the $z\approx 6$ QSO CFHQS J164121+375520
• A supermassive black hole under the radar: Repeating X-ray variability in a Seyfert galaxy
• What We Have Learned from NICER About Neutron Star Radii
• A radio, optical, UV and X-ray view of the enigmatic changing look Active Galactic Nucleus 1ES~1927+654 from its pre- to post-flare states
• X-ray emission of radio-loud quasar SDSS J121426.52+140258.9: independent variations between optical/UV and X-ray emission