The transient event in NGC 1566 from 2017 to 2019 -- I. An eccentric accretion disk and a turbulent, disk-dominated broad-line region unveiled by double-peaked Ca II and O I lines

Abstract

NGC 1566 is known for exhibiting recurrent outbursts, which are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported to be accompanied by a change in Seyfert classification from Seyfert 1.8 to Seyfert 1.2. We analyze data from an optical spectroscopic variability campaign of NGC 1566 taken with the 9.2m SALT between July 2018 and October 2019 and supplement our data set with optical to near-infrared spectroscopic archival data taken by VLT/MUSE in September 2015 and October 2017. We observe the emergence and fading of a strong power-law-like blue continuum as well as strong variations in the Balmer, HeI, HeII lines and the coronal lines [FeVII], [FeX] and [FeXI]. Moreover, we detect broad double-peaked emission line profiles of OI 8446 and the CaII 8498,8542,8662 triplet. This is the first time that genuine double-peaked OI 8446 and CaII 8498,8542,8662 emission in AGN is reported in the literature. All broad lines show a clear redward asymmetry with respect to their central wavelength and we find indications for a significant blueward drift of the total line profiles during the transient event. We show that the double-peaked emission line profiles are well approximated by emission from a low-inclination, relativistic eccentric accretion disk, and that single-peaked profiles can be obtained by broadening due to scale-height dependent turbulence. Small-scale features in the OI and CaII lines suggest the presence of inhomogeneities in the broad-line region. We conclude that the broad-line region in NGC 1566 is dominated by the kinematics of a relativistic eccentric accretion disk. The broad-line region can be modeled to be vertically stratified with respect to scale-height turbulence. The observed blueward drift might be attributed to a low-optical-depth wind launched during the transient event.

arXiv comment22 pages, 17 figures. Published in Astronomy & Astrophysics (A&A 686, A17 (2024))

References in corpus (88)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• 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
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
• A Cosmology Calculator for the World Wide Web
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei
• AGN Black Hole Masses and Bolometric Luminosities
• Supermassive Black Holes in Active Galactic Nuclei. II. Calibration of the M-sigma Relationship for AGNs
• The Indo-U.S. Library of Coude Feed Stellar Spectra
• Locally Optimally Emitting Clouds and the Origin of Quasar Emission Lines
• A Systematic Search for Changing-Look Quasars in SDSS
• Modeling reverberation mapping data II: dynamical modeling of the Lick AGN Monitoring Project 2008 dataset
• The origin of the Broad Line Region in Active Galactic Nuclei
• A spectrophotometric atlas of Narrow-Line Seyfert 1 galaxies
• Completion of a Survey and Detailed Study of Double-Peaked Emission Lines in Radio-Loud AGNs
• Understanding X-ray reflection emissivity profiles in AGN: Locating the X-ray source
• Changing look: from Compton-thick to Compton-thin, or the re-birth of fossil AGN
• Explaining changing-look AGN with state transition triggered by rapid mass accretion rate drop
• Double-Peaked Low-Ionization Emission Lines in Active Galactic Nuclei
• Quasar Accretion Disks Are Strongly Inhomogeneous
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• 1ES 1927+654: An AGN Caught Changing Look on a Timescale of Months
• Evolution of Broad-line Emission from Active Galactic Nuclei
• A Mid-IR Selected Changing-Look Quasar and Physical Scenarios for Abrupt AGN Fading
• The ASAS-SN Catalog of Variable Stars III: Variables in the Southern TESS Continuous Viewing Zone
• Average Quasar Spectra in the Context of Eigenvector 1
• Evolution of the Nuclear Accretion Disk Emission in NGC 1097: Getting Closer to the Black Hole
• A possible mechanism for multiple changing look phenomenon in Active Galactic Nuclei
• Extreme AGN variability: evidence of magnetically elevated accretion?
• The Lack of BLR in Low Accretion Rate AGN as Evidence of their Origin in the Accretion Disk
• The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei -- I. The Observations
• A new physical interpretation of optical and infrared variability in quasars
• The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
• Understanding extreme quasar optical variability with CRTS: II. Changing-state quasars
• Quasar Viscosity Crisis
• Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic Nuclei
• A new class of flares from accreting supermassive black holes
• Reverberation Mapping and the Disk Wind Model of the Broad Line Region
• Velocity-resolved reverberation mapping of five bright Seyfert 1 galaxies
• Evidence For A Precessing Accretion Disk in the Nucleus of NGC 1097
• The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad-Line Region
• Long-Term Profile Variability in Active Galactic Nuclei with Double-Peaked Balmer Emission Lines
• New changing look case in NGC 1566
• Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548
• The Tidal Disruption Event AT 2018hyz I: Double-peaked emission lines and a flat Balmer decrement
• The shape of broad-line profiles in AGN
• Double-Peaked Balmer Emission Indicating Prompt Accretion Disk Formation in an X-Ray Faint Tidal Disruption Event
• The detection and X-ray view of the changing look AGN HE 1136-2304
• Modified models of radiation pressure instability in application to 10, 10${}^5$, and 10${}^7$ $M_{\odot }$ accreting black holes
• The formerly X-ray reflection-dominated Seyfert~2 galaxy NGC6300
• Disk origin of broad optical emission lines of the TDE candidate PTF09djl
• Observations of OI and CaII Emission Lines in Quasars: Implications for the Site of FeII Line Emission
• Distinguishing Tidal Disruption Events from Impostors
• Opacity Driven Convection and Variability in Accretion Disks around Supermassive Black Holes
• Infrared FeII Emission in Narrow-Line Seyfert 1 Galaxies
• Low-Ionization Emission Regions in Quasars: Gas Properties Probed with Broad O I and Ca II Lines
• Vertical broad-line region structure in nearby active galactic nuclei
• An elliptical accretion disk following the tidal disruption event AT 2020zso
• WALLABY Early Science - III. An HI Study of the Spiral Galaxy NGC 1566
• Changing-look active galactic nuclei: close binaries of supermassive black holes in action
• Variability of the H-beta line profiles as an indicator of orbiting bright spots in accretion disks of quasars: a case study of 3C 390.3
• The CaFe Project: Optical Fe II and Near-Infrared Ca II triplet emission in active galaxies -- simulated EWs, the co-dependence of cloud sizes and metal content
• Spectral optical monitoring of the double peaked emission line AGN Arp 102B: II. Variability of the broad line properties
• The nuclear gas disk of NGC 1566 dissected by SINFONI and ALMA
• OI and CaII observations in intermediate redshift quasars
• Observed trend in the star formation history and the dark matter fraction of galaxies at redshift $z\approx 0.8$
• NGC 1566: analysis of the nuclear region from optical and near-infrared Integral Field Unit spectroscopy
• The "red shelf" of the Hb line in the Seyfert 1 galaxies RXS J01177+3637 and HS 0328+05
• Broad-line region structure and line profile variations in the changing look AGN HE1136-2304
• Broad-line Region of the Quasar PG 2130+099 from a Two-Year Reverberation Mapping Campaign with High Cadence
• The CaFe Project: Optical Fe II and Near-Infrared Ca II triplet emission in active galaxies: (I) Photoionization modelling
• The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566
• The OI Line Emission in Active Galactic Nuclei Revisited
• AT 2021loi: A Bowen Fluorescence Flare with a Rebrightening Episode, Occurring in a Previously-Known AGN
• Panchromatic Properties of the Extreme FeII Emitter PHL 1092
• Simultaneous H alpha and dust reverberation mapping of 3C120: Testing the bowl-shaped torus geometry
• Long-term optical, UV, and X-ray continuum variations in the changing-look AGN HE 1136-2304
• Short-Timescale monitoring of the X-ray, UV and broad double-peak emission line of the nucleus of NGC 1097
• The outburst of the changing-look AGN IRAS23226-3843 in 2019
• Anomalous Broad-Line Region Responses to Continuum Variability in Active Galactic Nuclei. I. H$\beta$ Variability
• Spiral Arms in Broad-line Regions of Active Galactic Nuclei. I. Reverberation and Differential Interferometric Signals of Tightly Wound Cases
• Spiral Arms in Broad-line Regions of Active Galactic Nuclei. II. Loosely Wound Cases: Reverberation Properties
• First observation of double-peaked O I emission in the near-infrared spectrum of an active galaxy
• Detection of a double-peaked H$\alpha$ component from the accretion disc of NGC 4958
• Periodic optical variability of AGN

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