J/ApJ/910/125ivo://CDS.VizieR/J/ApJ/910/125doi:10.26093/cds/vizier.19100125CDSPayne A.V.Shappee B.J.Hinkle J.T.Vallely P.J.Kochanek C.S.,Holoien T.W.-S.Auchettl K.Stanek K.Z.Thompson T.A.Neustadt J.M.M.,Tucker M.A.Armstrong J.D.Brimacombe J.Cacella P.Cornect R.,Denneau L.Fausnaugh M.M.Flewelling H.Grupe D.Heinze A.N.,Lopez L.A.Monard B.Prieto J.L.Schneider A.C.Sheppard S.S.,Tonry J.L.Weiland H.2022-11-25T13:14:33Z2022-10-10T09:09:02ZCDS support team

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

cds-question@unistra.frseyfert-galaxiesultraviolet-photometryinfrared-photometryvisible-astronomyWide-band photometryx-ray-sourcessurveysactive-galactic-nucleiWe present the discovery that ASASSN-14ko is a periodically flaring active galactic nucleus at the center of the galaxy ESO 253-G003. At the time of its discovery by the All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as a supernova close to the nucleus. The subsequent 6yr of V- and g-band ASAS-SN observations revealed that ASASSN-14ko has nuclear flares occurring at regular intervals. The 17 observed outbursts show evidence of a decreasing period over time, with a mean period of P_0_=114.2+/-0.4days and a period derivative of dP/dt=-0.0017+/-0.0003. The most recent outburst in 2020 May, which took place as predicted, exhibited spectroscopic changes during the rise and had a UV bright, blackbody spectral energy distribution similar to tidal disruption events (TDEs). The X-ray flux decreased by a factor of 4 at the beginning of the outburst and then returned to its quiescent flux after ~8days. The Transiting Exoplanet Survey Satellite observed an outburst during Sectors 4-6, revealing a rise time of 5.60+/-0.05days in the optical and a decline that is best fit with an exponential model. We discuss several possible scenarios to explain ASASSN-14ko's periodic outbursts, but currently favor a repeated partial TDE. The next outbursts should peak in the optical on UT 2020 September 7.4+/-1.1 and UT 2020 December 26.5+/-1.4.2021ApJ...910..125Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/910/125CatalogResearchIsServedByTAP VizieR generic servicerelated-toVII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/ApJS/132/37 : Spectroscopy of Southern warm IR galaxies (Kewley+, 2001)J/ApJ/560/566 : K-band galaxy LF from 2MASS (Kochanek+, 2001)J/ApJ/676/944 : GALEX & CFHTLS cand. tidal disruption events (Gezari+, 2008)J/ApJ/687/1201 : SN and LGRB locations in their host galaxies (Kelly+, 2008)J/A+A/480/611 : XMM-Newton slew survey catalogue, XMMSL1 (Saxton+, 2008)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJS/207/19 : Hard X-ray survey from Swift-BAT 6yrs (Baumgartner+, 2013)J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)J/ApJS/210/3 : SDSS bulge, disk & stellar mass estimates (Mendel+, 2014)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (Sullivan+, 2015)J/ApJ/821/56 : Space telescope RM project. III. NGC5548 (Fausnaugh+, 2016)J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)J/MNRAS/455/2918 : Phot. & line luminosities for ASASSN-14li (Holoien+, 2016)J/MNRAS/464/2672 : ASAS-SN bright supernova catalog 2013-2014 (Holoien+, 2017)J/ApJ/836/99 : NuSTAR serendipitous survey: 40-month cat. (Lansbury+, 2017)J/ApJ/880/120 : Phot. of the tidal disruption event PS18kh (Holoien+, 2019)J/ApJ/883/111 : UV-Opt LCs of ASASSN-19bt detected by TESS (Holoien+, 2019)J/ApJ/883/94 : Optical & UV follow-up of 1ES 1927+654 (Trakhtenbrot+, 2019)J/ApJ/898/161 : 500days of ASASSN-18pg multiwavelength obs. (Holoien+, 2020)J/ApJ/908/51 : TESS early LCs of type Ia Supernovae (Fausnaugh+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/910/125https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/910/125http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/910/125https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/910/125https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/910/125http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/910/125GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayUVOpticalInfrareddefaultJ/ApJ/910/125/table1Photometry of ASASSN-14ko used in this analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJD[2456790.49/2459000.21] Julian Date of observationdtime.epochdoubleBandBand/Instrument used (1)meta.code;instr.filtercharFlambda[-2.21e-15/3.2e-12] Fluxphot.flux.densitydoublee_Flambda[3.14e-18/3.9e-13] Uncertainty for Flambdastat.errordoublex_FlambdaUnits for Flambda (2)meta.unitchar