J/AJ/159/245ivo://CDS.VizieR/J/AJ/159/245doi:10.26093/cds/vizier.51590245CDSWang J.Xu D.W.Sun S.S.Feng Q.C.Li T.R.Xiao P.F.Wei J.Y.2021-03-23T12:32:42Z2020-07-23T12:52:36ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fractive-galactic-nucleiblack-holesseyfert-galaxiesvisible-astronomyspectroscopyThe discovery of spectral type transition of active galactic nuclei (AGNs), the so-called "changing-look" (CL) phenomenon, challenges the widely accepted AGN paradigm, not only in the orientation-based unified model, but also in the standard disk model. In past decades, only a couple of nearby repeat changing-look active galactic nuclei (CL-AGNs) have been identified. Here we report spectroscopic observations of UGC3223 over the course of 18yr, from 2001 onwards. Combining the spectrum taken in 1987 by Stirpe, we have witnessed its type transitions from 1.5 to 2.0 to 1.8 over 32yr, and captured a long-lived (at least 10 yr) thorough "turn-off" state with a spectrum typical of a Seyfert 2 galaxy. The long-term thorough turn-off state probably suggests a once-dormant and an awakening central engine in UGC3223. We argue that the (dis)appearance of the broad Balmer emission lines can be explained by the disk-wind broad-line region model given the evolution of the calculated Eddington ratio of accretion of the supermassive black hole.2020AJ....159..245Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/159/245CatalogResearchIsServedByTAP VizieR generic servicerelated-toIII/116 : Spectrophotometric Standards (Massey+ 1988)VII/248 : Quasars and Active Galactic Nuclei (12th Ed.) (Veron+ 2006)J/ApJ/670/92 : New sample of low-mass black holes in AGN (Greene+, 2007)J/A+A/545/A15 : AMIGA XI. Optical nuclear activity (Sabater+, 2012)J/ApJ/755/167 : Low-mass black holes in SDSS Seyfert 1 galaxies (Dong+, 2012)J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/ApJ/794/75 : HST-COS UV spectra observations of AGNs (Stevans+, 2014)J/ApJ/806/22 : SEAMBHs IV. H{beta} time lags (Du+, 2015)J/A+A/596/A64 : 4 AGN optical spectra (Simmonds+, 2016)J/ApJS/226/11 : IR spectroscopy of AGN & starbursts (Samsonyan+, 2016)J/ApJ/854/160 : SDSS & DES long-term extreme variability QSOs (Rumbaugh+, 2018)J/ApJ/870/123 : Swift optical & UV flux of four AGNs (Edelson+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/159/245https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/159/245http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/159/245https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/159/245https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/159/245http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/159/245GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/159/245/figure1Combined table from original tablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[3457/8587] Spectrum wavelength0.1nmem.wldoublefluxFlux, erg/s/cm2/AngstromscW.m**-2.nm**-1phot.fluxdoubleDateDate of the observation'date'time.epochchar