J/ApJ/953/32ivo://CDS.VizieR/J/ApJ/953/32doi:10.26093/cds/vizier/ba-xs-10CDSMakrygianni L.Trakhtenbrot B.Arcavi I.Ricci C.Lam M.C.Horesh A.,Sfaradi I.Bostroem K.A.Hosseinzadeh G.Howell D.A.Pellegrino C.,Fender R.Green D.A.Williams D.R.A.Bright J.2026-07-02T12:00:21Z2025-11-03T16:08:25ZCDS support team

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

cds-question@unistra.frtransient-sourcesinfrared-photometryvisible-astronomybroad-band-photometryspectroscopyThe optical-ultraviolet transient AT 2021loi is located at the center of its host galaxy. Its spectral features identify it as a member of the Bowen fluorescence flare (BFF) class. The first member of this class was considered to be related to a tidal disruption event, but enhanced accretion onto an already active supermassive black hole was suggested as an alternative explanation. Having occurred in a previously known unobscured active galactic nucleus, AT 2021loi strengthens the latter interpretation. Its light curve is similar to those of previous BFFs, showing a rebrightening approximately 1yr after the main peak (which was not explicitly identified but might be the case in all previous BFFs). An emission feature around 4680{AA}, seen in the preflare spectrum, strengthens by a factor of ~2 around the optical peak of the flare and is clearly seen as a double-peaked feature then, suggesting a blend of NIII{lambda}4640 with HeII{lambda}4686 as its origin. The appearance of OIII{lambda}3133 and possible NIII{lambda}{lambda}4097,4103 (blended with H{delta}) during the flare further support a Bowen fluorescence classification. Here we present ZTF, ATLAS, Keck, Las Cumbres Observatory, NEOWISE-R, Swift AMI, and Very Large Array observations of AT 2021loi, making it one of the best-observed BFFs to date. It thus provides some clarity on the nature of BFFs but also further demonstrates the diversity of nuclear transients.2023ApJ...953...32Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/953/32CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/328 : AllWISE Data Release (Cutri+ 2013)VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)J/ApJ/680/169 : SDSS DR5 virial black hole masses (Shen+, 2008)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/ApJ/753/106 : QSO variability with SDSS and POSS imaging (MacLeod+, 2012)J/MNRAS/429/3330 : AMI Galactic Plane Survey at 16GHz. I. (Perrott+, 2013)J/ApJ/779/109 : Long-term monitoring of NGC 5548 (Peterson+, 2013)J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)J/ApJ/788/159 : 17 Seyfert 1 galaxies light curves (Koshida+, 2014)J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)J/ApJ/805/122 : X-ray properties of PHL1811 analogs and WLQs (Luo+, 2015)J/A+A/588/A103 : 2nd ROSAT all-sky survey (2RXS) source cat. (Boller+, 2016)J/ApJ/819/154 : SDSS-DR7 QSOs with X-ray and UV luminosities (Lusso+, 2016)J/MNRAS/459/3939 : Type II supernova light curves (Valenti+, 2016)J/ApJ/844/46 : Phot. of the transient event iPTF16fnl (Blagorodnova+, 2017)J/ApJS/233/17 : Swift/BAT AGN spectroscopic survey. V. X-ray (Ricci+, 2017)J/ApJS/234/23 : The WISE AGN candidates catalogs (Assef+, 2018)J/ApJ/854/160 : SDSS & DES long-term extreme var. QSOs (Rumbaugh+, 2018)J/ApJ/874/8 : Follow-up sp. of SDSS changing-look QSOs (Macleod+, 2019)J/ApJ/883/94 : Optical & UV follow-up of 1ES 1927+654 (Trakhtenbrot+, 2019)J/ApJ/872/198 : UV-Opt LC of flare AT2018zr (van Velzen+, 2019)J/MNRAS/491/4925 : Changing-state quasars with CRTS (Graham+, 2020)J/ApJS/249/17 : SDSS QSO DR14 spectral properties (Rakshit+, 2020)J/ApJS/261/5 : BASS. XXV. DR2 AGNs BH masses (Mejia-Restrepo+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/953/32https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/953/32http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/953/32https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/953/32https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/953/32http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/953/32GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/ApJ/953/32/table2Photometry of AT 2021loirecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[59341.4/59969.2] Modified Julian Date (JD-2400000.5)dtime.epochdoubleFiltDescription of Filtermeta.notecharmag[16.3/19.52]? AB magnitude in Filtmagphot.magfloatnullablee_mag[0/0.3]? Uncertainty in magmagstat.error;phot.magfloatnullableTelSource (Telescope) for mag (1)meta.id;instr.telcharJ/ApJ/953/32/table4Optical spectroscopy of AT 2021loirecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[56648/59839.6] Modified Julian Date (JD-2400000.5)dtime.epochdoubleTelTelescope/Instrument usedmeta.id;instr.telcharR[500/1800] Approximate resolving power of the spectrumspect.resolutionintFHb[10/79] Flux, H{beta}, 10^-15^erg/s/cm21e-18W.m**-2phot.flux;spect.line;em.line.Hbetafloate_FHb[0.5/9.2] Uncertainty in FHb1e-18W.m**-2stat.error;phot.flux;em.line.HbetafloatFBF[5.8/56] Flux, double peaked emission feature, 10^-15^erg/s/cm2 (1)1e-18W.m**-2phot.flux;spect.linefloate_FBF[0.2/3] Uncertainty in FBF (1)1e-18W.m**-2stat.error;phot.flux;spect.linefloatFOIII[1/4.2] Flux, [O III] 5007 Angstroms, 10^-15^erg/s/cm21e-18W.m**-2phot.flux;spect.line;em.line.OIIIfloate_FOIII[0.02/0.3] Uncertainty in FOIII1e-18W.m**-2stat.error;phot.flux;em.line.OIIIfloatlogL5100[42.46/43.7] Log, Luminosity at 5100{AA} continuum, erg/slog(1e-07W)phys.luminosity;em.optfloatFWHM[1917/3024] Full-width at half-max, H{beta}km/sspect.line.width;em.line.Hbetainte_FWHM[31/528] Uncertainty in FWHMkm/sstat.error;spect.line.width;em.line.Hbetaint