J/MNRAS/463/296ivo://CDS.VizieR/J/MNRAS/463/296doi:10.26093/cds/vizier.74630296CDSLawrence A.Bruce A.G.MacLeod C.Gezari S.Elvis M.Ward M.,Smartt S.J.Smith K.W.Wright D.Fraser M.Marshall P.Kaiser N.,Burgett W.Magnier E.Tonry J.Chambers K.Wainscoat R.Waters C.,Price P.Metcalfe N.Valenti S.Kotak R.Mead A.Inserra C.,Chen T.W.Soderberg A.2024-08-16T20:19:12Z2018-06-12T12:16:22ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleiquasarsvisible-astronomysloan-photometryline-intensitiesWe discuss 76 large amplitude transients ({Delta}m>1.5) occurring in the nuclei of galaxies, nearly all with no previously known active galactic nucleus (AGN). They have been discovered as part of the Pan-STARRS1 (PS1) 3{pi} survey, by comparison with Sloan Digital Sky Survey (SDSS) photometry a decade earlier, and then monitored with the Liverpool Telescope, and studied spectroscopically with the William Herschel Telescope (WHT). Based on colours, light-curve shape, and spectra, these transients fall into four groups. A few are misclassified stars or objects of unknown type. Some are red/fast transients and are known or likely nuclear supernovae. A few are either radio sources or erratic variables and so likely blazars. However the majority (~66 per cent) are blue and evolve slowly, on a time-scale of years. Spectroscopy shows them to be AGN at z ~0.3-1.4, which must have brightened since the SDSS photometry by around an order of magnitude. It is likely that these objects were in fact AGN a decade ago, but too weak to be recognized by SDSS; they could then be classed as 'hypervariable' AGN. By searching the SDSS Stripe 82 quasar database, we find 15 similar objects. We discuss several possible explanations for these slow-blue hypervariables - (i) unusually luminous tidal disruption events; (ii) extinction events; (iii) changes in accretion state; and (iv) large amplitude microlensing by stars in foreground galaxies. A mixture of explanations (iii) and (iv) seems most likely. Both hold promise of considerable new insight into the AGN phenomenon.2016MNRAS.463..296Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/463/296CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/463/296https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/463/296http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/463/296https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/463/296https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/463/296http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/463/296GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/463/296/sample (Basic properties (table A1) and cross-identifications (table A2))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/463/296/sample?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/463/296/sample?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/463/296/sample?GETtext/xml+votable180.050000true21.308708348.09772220.0055555555555555566/419 1010 2841 4122 4147 4166 4272 4412 4544 4606 4658 4815 4849 4909 4914 4995 5238 5516 5902 6046 6126 6142 6226 6407 7220 7324 7501 7562 8220 8248 8329 8475 8700 8778 8973 9597 9982 10224 10255 10705 11325 11532 11795 11806 11947 15594 17308 17316 18178 18625 19035 23050 23417 24533 26052 26608 26941 26946 27048 27397 27415 27442 27721 27915 28047 28122 28294 28522 28667 31397 31575 31618 31629 31907 32404https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/463/296?format=asciiOpticaldefaultJ/MNRAS/463/296/sampleBasic properties (table A1) and cross-identifications (table A2)SimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPS1Display the Pan-STARRS 1 data (Chambers et al., 2016, Cat. II/349)meta.ref.urlcharNameUsual short name (G1)meta.idcharTransientTransient IDmeta.id;meta.maincharRAJ2000Right ascension (J2000.0)pos.eq.ra;meta.mainDEJ2000Declination (J2000.0)pos.eq.dec;meta.mainFDateDate of flagtime.epochnullableWDateWHT Observation Datetime.epochnullableSDSSSDSS ID (JHHMMSS.ss+DDMMSS.s)meta.idcharUKIDSS? UKIDSS ID (Lawrence et al., 2007MNRAS.379.1599L, Cat. II/314)meta.idnullablen_UKIDSS[oi] Note when no UKIDSS ID (1)meta.notecharNVSS? NVSS ID (Condon et al., 1998AJ....115.1693C, Cat. VIII/65)meta.idintnullableCRTSCRTS ID (Drake et al., 2009, Cat. J/ApJ/696/870)meta.idcharJ/MNRAS/463/296/tablea3Host and transient photometryNameHost galaxy name (G1)meta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintgmagHost Galaxy g magnitude (1)magphot.mag;em.opt.Bfloate_gmagrms uncertainty on gmagmagstat.error;phot.magfloatu-gHost Galaxy u-g colour index (1)magphot.color;em.opt.U;em.opt.Bfloate_u-grms uncertainty on u-gmagstat.errorfloatg-rHost Galaxy g-r colour index (1)magphot.color;em.opt.B;em.opt.Rfloate_g-rrms uncertainty on g-rmagstat.error;phot.color;em.opt.Bfloatr-iHost Galaxy r-i colour index (1)magphot.color;em.opt.R;em.opt.Ifloate_r-irms uncertainty on r-imagstat.error;phot.color;em.opt.RfloatgmaxTTransient maximum g magnitude (2)magphot.mag;em.opt.Bfloatl_u-gTLimit flag on u-gTmeta.code.errorcharu-gT? Transient u-g colour index (2)magphot.color;em.opt.U;em.opt.Bfloatnullablee_u-gT? rms uncertainty on u-gTmagstat.errorfloatnullableg-rTTransient g-r colour index (2)magphot.color;em.opt.B;em.opt.Rfloate_g-rTrms uncertainty on g-rTmagstat.errorfloatJ/MNRAS/463/296/tablea4Various quantities derived from the light curves, spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameUsual short name (G1)meta.idcharctype[1/3]? Colour type (1)meta.codeintnullableAmpgTransient amplitude in g band (2)magsrc.var.amplitudefloate_Ampgrms uncertainty on Ampgmagstat.errorfloatSpTypeSpectral typesrc.spTypecharzsp? Spectroscopic redshiftsrc.redshiftfloatnullablezph? Photometric redshift, from SDSS DR7src.redshiftfloatnullablee_zph? rms uncertainty on sphstat.errorfloatnullableSlopeEarly decay ratemag.month**-1arith.ratefloate_Sloperms uncertainty on Slopemag.month**-1stat.errorfloatSlopeAGN? Slope in the AGN rest frame, i.e. multiplied by 1=zarith.ratefloatnullableNoteNotes (3)meta.notecharJ/MNRAS/463/296/tablea5Quantities measured from the WHT spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameUsual short name (G1)meta.idcharzRedshiftsrc.redshiftdoubleF(MgII)MgII flux1e-18W.m**-2phot.fluxfloate_F(MgII)rms uncertainty on F(MgII)1e-18W.m**-2stat.errorfloatF(MgIIc)Continuum MgII flux1e-18W.m**-2phot.fluxfloatEW(MgII)AGN rest-frame MgII equivalent width0.1nmspect.line.eqWidthfloatl_F(OII)Limit flag on F(OII)meta.code.errorcharF(OII)? OII flux1e-18W.m**-2phot.fluxfloatnullablee_F(OII)? rms uncertainty on F(OII)1e-18W.m**-2stat.errorfloatnullableF(OIIc)? Continuum OII flux1e-18W.m**-2phot.fluxfloatnullablel_EW(OII)Limit flag on EW(OII)meta.code.errorcharEW(OII)? AGN rest-frame OII equivalent width0.1nmspect.line.eqWidthfloatnullablel_F(OIII)Limit flag on F(OIII)meta.code.errorcharF(OIII)? OIII flux1e-18W.m**-2phot.fluxfloatnullablee_F(OIII)? rms uncertainty on F(OIII)1e-18W.m**-2stat.errorfloatnullableF(OIIIc)? Continuum OIII flux1e-18W.m**-2phot.fluxfloatnullablel_EW(OIII)Limit flag on EW(OIII)meta.code.errorcharEW(OIII)? AGN rest-frame OIII equivalent width0.1nmspect.line.eqWidthfloatnullable