J/ApJ/926/142ivo://CDS.VizieR/J/ApJ/926/142doi:10.26093/cds/vizier.19260142CDSPayne A.V.Shappee B.J.Hinkle J.T.Holoien T.W.-S.Auchettl K.,Kochanek C.S.Stanek K.Z.Thompson T.A.Tucker M.A.Armstrong J.D.,Boyd P.T.Brimacombe J.Cornect R.Huber M.E.Jha S.W.Lin C.-C.2023-12-14T01:23:00Z2023-11-22T13:24:19ZCDS support team

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

cds-question@unistra.frtransient-sourcesultraviolet-photometryx-ray-sourcesvisible-astronomyspectroscopyASASSN-14ko is a recently discovered periodically flaring transient at the center of the active galactic nucleus (AGN) ESO 253-G003 with a slowly decreasing period. Here, we show that the flares originate from the northern, brighter nucleus in this dual-AGN, post-merger system. The light curves for the two flares that occurred in 2020 May and September are nearly identical over all wavelengths. For both events, Swift observations showed that the UV and optical wavelengths brightened in unison. The effective temperature of the UV/optical emission rises and falls with the increase and subsequent decline in the luminosity. The X-ray flux, by contrast, first rapidly drops over ~2.6 days, rises for ~5.8 days, drops again over ~4.3 days, and then recovers. The X-ray spectral evolution of the two flares differ, however. During the 2020 May peak the spectrum softened with increases in the X-ray luminosity, while we observed the reverse for the 2020 September peak. We found a small change in the period derivative, which seems to indicate that the system does not have a static period derivative and there is some stochasticity in its evolution.2022ApJ...926..142Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/926/142CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/ApJ/613/682 : AGN central masses & broad-line region sizes (Peterson+, 2004)J/ApJ/687/1201 : SN and LGRB locations in their host galaxies (Kelly+, 2008)J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)J/MNRAS/455/2918 : Phot. & line luminosities for ASASSN-14li (Holoien+, 2016)J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)J/ApJ/883/94 : Optical and UV follow-up of 1ES 1927+654 (Trakhtenbrot+, 2019)J/ApJ/898/161 : 500days of ASASSN-18pg multiwavelength obs. (Holoien+, 2020)J/ApJ/910/83 : Swift phot. recomputed for 38 transients (Hinkle+, 2021)J/ApJ/910/125 : Follow-up photometry of ASASSN-14ko (Payne+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/926/142https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/926/142http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/926/142https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/926/142https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/926/142http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/926/142GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayUVOpticaldefaultJ/ApJ/926/142/table1Light curve data of ASASSN-14ko used in this analysisrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJD[2448102.27/2459113.72] Julian Datedtime.epochdoubleBandObservational passbandinstr.bandpasscharn_BandDescription of Band (1)meta.notecharl_LumUpper limit flag on Lummeta.code.errorcharLum? Luminosity in Band; erg/s1e-07Wphys.luminositydoublenullablee_Lum? Uncertainty in Lum1e-07Wstat.errordoublenullablel_HRUpper limit flag on HRmeta.code.errorcharHR[-0.7/0.61]? Hardness ratio: HR=(H-S)/(H+S) (2)phot.flux;arith.ratiodoublenullablee_HR[0.002/0.8]? Uncertainty in Lumstat.errordoublenullableJ/ApJ/926/142/fig4The SALT ASASSN-14ko spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs[1/2] Spectrum identifier (1)meta.codeintlambda[3493.1/7258.3] Wavelength; Angstroms0.1nmem.wldoubleFlux[9.7e-16/1.1e-14] Flux; erg/s/cm^2^/{AA}cW.m**-2.nm**-1phot.fluxdouble