J/ApJ/874/8ivo://CDS.VizieR/J/ApJ/874/8doi:10.26093/cds/vizier.18740008CDSMacLeod C.L.Green P.J.Anderson S.F.Bruce A.Eracleous M.Graham M.,Homan D.Lawrence A.Lebleu A.Ross N.P.Ruan J.J.Runnoe J.,Stern D.Burgett W.Chambers K.C.Kaiser N.Magnier E.Metcalfe N.2021-03-23T13:03:21Z2020-09-07T08:29:46ZCDS support team

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

cds-question@unistra.frquasarsvisible-astronomyspectroscopyredshiftedsloan-photometryActive galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, changing-look quasars (CLQs). These surprisingly large and sometimes rapid transitions challenge accepted models of quasar physics and duty cycles, offer several new avenues for study of quasar host galaxies, and open a wider interpretation of the cause of differences between broad and narrow-line AGN. To better characterize extreme quasar variability, we present follow-up spectroscopy as part of a comprehensive search for CLQs across the full Sloan Digital Sky Survey (SDSS) footprint using spectroscopically confirmed quasars from the SDSS DR7 catalog. Our primary selection requires large-amplitude (|{Delta}g|>1mag, |{Delta}r|>0.5mag) variability over any of the available time baselines probed by the SDSS and Pan-STARRS 1 surveys. We employ photometry from the Catalina Sky Survey to verify variability behavior in CLQ candidates where available, and confirm CLQs using optical spectroscopy from the William Herschel, MMT, Magellan, and Palomar telescopes. For our adopted signal-to-noise ratio threshold on variability of broad H{beta} emission, we find 17 new CLQs, yielding a confirmation rate of >~20%. These candidates are at lower Eddington ratio relative to the overall quasar population, which supports a disk-wind model for the broad line region. Based on our sample, the CLQ fraction increases from 10% to roughly half as the continuum flux ratio between repeat spectra at 3420{AA} increases from 1.5 to 6. We release a catalog of more than 200 highly variable candidates to facilitate future CLQ searches.2019ApJ...874....8Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/874/8CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)IX/55 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR8 (XMM-SSC, 2018)VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)J/AJ/126/1720 : ugriz and H{alpha} of double-peaked AGN (Strateva+, 2003)J/AJ/126/2209 : X-ray AGN from RASS and SDSS (Anderson+, 2003)J/ApJ/613/682 : AGN central masses & broad-line region sizes (Peterson+, 2004)J/ApJ/663/81 : SED of hard X-ray selected AGN in XMDS (Polletta+, 2007)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/ApJ/818/30 : Lag measurements for 15 z<0.8 QSOs from SDSS-RM (Shen+, 2016)J/ApJ/821/33 : Broad H{beta} emission line in 102 Seyfert gal. (Runco+, 2016)J/ApJ/821/56 : Space telescope RM project. III. NGC5548 LCs (Fausnaugh+, 2016)J/ApJ/854/160 : SDSS & DES long-term extreme variability QSOs (Rumbaugh+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/874/8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/874/8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/874/8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/874/8https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/874/8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/874/8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/874/8/table2 (Changing-look quasar (CLQ) candidates)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/874/8/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/874/8/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/874/8/table2?GETtext/xml+votable180.050000true0.316653114.18976560.0055555555555555566/4104 4107 4216 4324 4327 4355 4453 4474 4688 4789 4792 4890 4895 4903 4951 5019 5071 5073 5076 5090 5111 5220 5232 5246 5286 5362 5363 5435 5490 5627 5644 5740 5754 5772 5779 5796 5801 5817 5828 5860 5879 5885 5922 5930 5941 5953 5985 6044 6045 6057 6062 6401 6420 6469 6473 6508 6530 6536 6543 6554 6566 6577 6614 7215 7225 7245 7248 7259 7287 7290 7298 7375 7439 7518 7588 8209 8289 8328 8482 8536 8599 8848 8852 8889 8970 9012 9062 9082 9093 9131 9149 9173 9174 9191 9227 9400 9462 9471 9613 9633 9648 9785 9842 9852 9870 9886 9941 9945 9952 9978 9986 9990 10016 10086 10098 10122 10192 10240 10252 10306 10403 10526 10663 10787 10865 10924 10928 10949 10951 11033 11086 11143 11181 11213 11346 11348 11446 11467 11470 11496 11592 11800 11839 11883 17240 17248 17250 17254 17293 17302 17320 17514 17515 17748 17749 17751 17763 17772 17819 18075 18096 18416 18599 18617 18766 18788 18838 18856 18865 18881 19021 19050 19110 19114 19200 19413 19663 19727 19737 20003 20005 21855 21887 23043 23189 23191 23197 25931 25956 26004 26014 26057 26073 26083 26254 26274 26281 26297 26322 26385 26397 26399 26420 26477 26621 26981 27043 27047 27063 27079 27231 27285 27334 27351 27355 27364 27370 27391 27442 27487 27506 27555 27585 27662 27715 27731 27742 27805 27848 27855 27894 27913 27928 27939 27945 28203 28288 28329 28394 28547 28602 28611 28615 28619 30039 31389 31437 31454 31457 31474 31535 32445 490143.588997330618193e-19 4.653515163505597e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/874/8?format=asciiOpticaldefaultJ/ApJ/874/8/table2Changing-look quasar (CLQ) candidatesTelFacility identifiermeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS identifier (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharprimarySplink to spectral decomposition (Table 3)meta.ref.urlcharz[0.15/0.82] Spectroscopic redshiftsrc.redshiftfloatEx?[0/1] Morphology flag (1=extended or 0=point source)meta.codeintMJD1p[51075/56031] Modified Julian Date of first photometric observationdtime.epochintgmag1[16.2/22] First SDSS g band (AB) magnitudemagphot.mag;em.opt.Bfloate_gmag1[0.005/0.1] Uncertainty in g1magmagstat.error;phot.magfloatMJD2p[53655/56588] Modified Julian Date of second photometric observationdtime.epochintgmag2[15.9/22.8] Second SDSS g band (AB) magnitudemagphot.mag;em.opt.Bfloate_gmag2[0.002/0.15] Uncertainty in g2magmagstat.error;phot.magfloatMJD1s[51630/55500] Modified Julian Date of first spectroscopic observationdtime.epochintMJDPS1[55242/56625] Modified Julian Date of PS1 observationdtime.epochintgmagPS1[15.9/22.7] Pan-STARRS 1 g band (AB) magnitudemagphot.mag;em.opt.Bfloate_gmagPS1[0.005/0.2] Uncertainty in gPS1magmagstat.errorfloatMJD2s[0/58367] Modified Julian Date of second spectroscopic observation (1)dtime.epochintCLQ?[0/1] Changing-look quasar by VI?meta.codeintNsigma[-1/11.9]? Flux deviation at H{beta}stat.stdev;phot.fluxfloatnullablePS1Display data from Pan-STARRS DR1 (II/349) within 1"meta.ref.urlcharSloanDisplay the online SDSS data for the nearest objectmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlcharNEDNED column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainJ/ApJ/874/8/table3Spectral decompositionrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS identifier (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharL3240-1[27/1595] Luminosity at 3240{AA} in first SDSS spectrum1e+35Wphys.luminosityfloate_L3240-1[0.5/47] Uncertainty in L3240-11e+35Wstat.errorfloatl_LHb-1Limit fl on l_LHb-1meta.code.errorcharLHb-1[0.14/20] Luminosity at H{beta} in first SDSS spectrum1e+35Wphys.luminosityfloate_LHb-1[0.03/2] Uncertainty in LHb-11e+35Wstat.errorfloatL3240-2[0/944] Luminosity at 3240{AA} in follow-up spectrum1e+35Wphys.luminosityfloate_L3240-2[0/38] Uncertainty in L3240-21e+35Wstat.errorfloatl_LHb-2Limit flag on LHb-2meta.code.errorcharLHb-2[0.05/15] Luminosity at H{beta} in follow-up spectrum1e+35Wphys.luminosityfloate_LHb-2[0/4] Uncertainty in LHb-21e+35Wstat.errorfloat