J/A+A/713/A69ivo://CDS.VizieR/J/A+A/713/A69CDSZhu L.Wang Z.Gupta A.C.Devanand P.U.Yang R.Huang Q.Lang M.,Li J.2026-09-04T08:18:31Z2026-09-04T09:17:34ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiquasarsspectroscopyvisible-astronomyChanging-look active galactic nuclei (CL-AGNs) challenge the unified model of AGNs and offer key insights into the physics of the accretion processes of super-massive black holes. While systematic spectroscopic comparisons have successfully identified large samples of CL-AGNs, photometric selection based on variability features provides an efficient alternative. We used the color-magnitude (CM) variability pattern method to continue our identification of the CL transition in AGNs. The resulting CL-AGN sample can help improve understanding of this phenomenon. The CM variability pattern method utilizes the slope (k) of the CM variations to identify strong "bluer-when-brighter" behavior, while the variation amplitudes in optical and mid-infrared (MIR) bands are also considered. The candidates selected from the Type-2 AGNs given in the Sloan Digital Sky Survey catalog were spectroscopically observed by us using the 3.6-m Devasthal Optical Telescope and the 2-m Himalayan Chandra Telescope. We successfully confirm seven turn-on CL-AGNs among 12 candidates in this work. Compared with both the general AGN populations and the spectroscopically identified CL-AGN sample, these CL-AGNs show larger optical and MIR variations and k values. The extreme CM variabilities of these sources (with optical magnitude changes >0.9) occurred recently. For four sources, flare-like brightening episodes were temporally associated with turn-on transitions within 3-7 years, suggesting that these flares may trace short-timescale accretion enhancement, central brightening, and broad-line region re-illumination. In addition, the estimated Eddington ratios for the confirmed CL-AGNs appear to cluster around a critical value of {lambda}_Edd_~0.01. The extreme CM variability serves as a highly efficient criterion for finding CL-AGNs. The properties of the CL-AGNs thus found suggest that they may represent AGNs at a pivotal state, which likely occurs in CL transitions due to enhanced accretion activity, while the cause of the accretion activity, which was determined to have a timescale of several years in this work, remains to be investigated further.2026A&A...713A..69Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/713/A69CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/713/A69https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/713/A69http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/713/A69https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/713/A69https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/713/A69http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/713/A69GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/713/A69/list (List of spectra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/713/A69/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/713/A69/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/713/A69/list?GETtext/xml+votable180.050000true26.66213.18588890.0055555555555555566/5918 6212 8305 10836 11000 11076 18299 26202 27123 27696 28197 31445https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/713/A69?format=asciiOpticaldefaultJ/A+A/713/A69/listList of spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName (JHHMMSS+DDMMSS)meta.id;meta.maincharRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintNyNumber of pixels along Y-axismeta.numberintObs.dateObservation datestime.epoch;obsnullablesizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharSNameSimbad namemeta.idcharSimbadSimbad column added by the CDSmeta.ref.urlchar