J/ApJ/930/12ivo://CDS.VizieR/J/ApJ/930/12doi:10.26093/cds/vizier.19300012CDSHinkle J.T.Holoien T.W.-S.Shappee B.J.Neustadt J.M.M.Auchettl K.,Vallely P.J.Shahbandeh M.Kluge M.Kochanek C.S.Stanek K.Z.,Huber M.E.Post R.S.Bersier D.Ashall C.Tucker M.A.Williams J.P.,de Jaeger T.Do A.Fausnaugh M.Gruen D.Hopp U.Myles J.,Obermeier C.Payne A.V.Thompson T.A.2024-11-06T20:25:15Z2024-04-25T09:58:35ZCDS support team

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

cds-question@unistra.frtransient-sourcesinfrared-photometryvisible-astronomybroad-band-photometryultraviolet-photometryx-ray-sourcesspectroscopyWe present observations of ASASSN-20hx, a nearby ambiguous nuclear transient (ANT) discovered in NGC 6297 by the All-Sky Automated Survey for Supernovae (ASAS-SN). We observed ASASSN-20hx from -30 to 275 days relative to the peak UV/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From Transiting Exoplanet Survey Satellite data, we determine that the ANT began to brighten on 2020 June 22.8 with a linear rise in flux for at least the first week. ASASSN-20hx peaked in the UV/optical 30 days later on 2020 July 22.8 (MJD=59052.8) at a bolometric luminosity of L=(3.15+/-0.04)x10^43^erg/s. The subsequent decline is slower than any TDE observed to date and consistent with many other ANTs. Compared to an archival X-ray detection, the X-ray luminosity of ASASSN-20hx increased by an order of magnitude to Lx~1.5x10^42^erg/s and then slowly declined over time. The X-ray emission is well fit by a power law with a photon index of {Gamma}~2.3-2.6. Both the optical and near-infrared spectra of ASASSN-20hx lack emission lines, unusual for any known class of nuclear transient. While ASASSN-20hx has some characteristics seen in both tidal disruption events and active galactic nuclei, it cannot be definitively classified with current data.2022ApJ...930...12Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/930/12CatalogResearchIsServedByTAP VizieR generic servicerelated-toII/267 : The SDSS Photometric Catalog, Release 4 (Adelman-McCarthy+, 2006)VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/ApJ/613/682 : AGN masses & broad-line region sizes (Peterson+, 2004)J/A+A/451/457 : X-ray properties of AGN in CDFS (Tozzi+, 2006)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJ/713/970 : Low-resolution SED templates for AGNs & gal. (Assef+, 2010)J/ApJ/716/993 : LAMP: reverberation mapping of H and He lines (Bentz+, 2010)J/ApJ/753/106 : Quasar variability with SDSS & POSS imaging (MacLeod+, 2012)J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)J/ApJS/210/3 : SDSS bulge, disk and stellar mass estimates (Mendel+, 2014)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/ApJ/799/208 : Type IIP supernovae from Pan-STARRS1 (Sanders+, 2015)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/A+A/596/A14 : Group catalogues of the local universe (Saulder+, 2016)J/ApJ/844/46 : Phot. of the transient event iPTF16fnl (Blagorodnova+, 2017)J/MNRAS/467/540 : BASS. IV. NIR lines & X-ray correlation (Lamperti+, 2017)J/ApJS/232/8 : 16yrs of AGNs X-ray sp. analyses from 7Ms CDF-S (Liu+, 2017)J/ApJS/233/17 : Swift/BAT AGN spectroscopic survey. V. X-ray (Ricci+, 2017)J/ApJ/852/72 : LFs of tidal disruption flares (van Velzen, 2018)J/ApJ/880/120 : Phot. of the tidal disruption event PS18kh (Holoien+, 2019)J/MNRAS/484/1899 : The ASAS-SN bright supernova catalogue - IV (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/903/31 : AT 2018hyz with Swift XRT, UVOT and Swope (Hung+, 2020)J/MNRAS/492/3073 : CALIFA galaxies hosting an AGN (Lacerda+, 2020)J/ApJ/901/61 : LCs of 4 superluminous SNe from the ZTF (Lunnan+, 2020)J/MNRAS/493/1044 : Nebular spectra of 111 Type Ia supernovae (Tucker+, 2020)J/ApJ/908/51 : TESS early LCs of type Ia Supernovae (Fausnaugh+, 2021)J/ApJ/910/83 : Swift phot. recomputed for 38 transients (Hinkle+, 2021)J/ApJ/910/125 : Follow-up photometry of ASASSN-14ko (Payne+, 2021)J/ApJS/255/7 : X-ray monitoring of 1ES 1927+654 (Ricci+, 2021)J/ApJ/926/142 : UV, optical & X-ray evolution of ASASSN-14ko (Payne+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/930/12https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/930/12http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/930/12https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/930/12https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/930/12http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/930/12GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayUVOpticalInfrareddefaultJ/ApJ/930/12/table3Host-subtracted photometry of ASASSN-20hxrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[59003/59327.4] Modified Julian Date of observation (JD-2400000.5)dtime.epochdoubledMJDhi[0/1.7] Range in MJD over which the data were stackeddtime.intervalfloatdMJDlo[0/2] Range in MJD over which the data were stackeddtime.intervalfloatFiltFilter (UVM2, UVW1, UVW2, UBV, ugriz, TESS)meta.id;instr.filtercharohsmag[15.69/21.3] Extinction-corrected, host-subtracted, AB-system magnitude in Filt (1)magphot.magfloate_ohsmag[0.02/0.4]? Uncertainty in ohsmag (1)magstat.error;phot.magfloatnullableJ/ApJ/930/12/table4X-ray luminosities and hardness ratios of ASASSN-20hxrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[58326.4/59346.3] Modified Julian Date of observation (JD-2400000.5)dtime.epochdoublelogLx[40.5/42.5] log, X-ray luminosity, 0.3-10keVlog(1e-07W)phys.luminosity;em.X-rayfloate_logLx[0/0.3] Uncertainty in logLxlog(1e-07W)stat.errorfloatHR[-0.9/1] Hardness ratio (1)phot.flux;arith.ratiofloate_HR[0/0.5] Uncertainty in HRstat.errorfloatSatSatellite ("Swift" or "NICER")meta.id;instr.telcharJ/ApJ/930/12/table6X-ray photon indicesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD[59051.3/59304] Modified Julian Date of observationdtime.epochdoubledMJD[2.2/35.2]? Range in MJD over which the Swift data were stackeddtime.intervalfloatnullableGamma[2/3.2] Photon index (1)meta.code;spect.indexfloate_Gamma[0.1/0.5] Uncertainty in Gammastat.errorfloatSatSatellitee ("Swift" or "NICER")meta.id;instr.telcharJ/ApJ/930/12/fig6*List of spectra included in subdirectory "sp"; table added by CDS (Data behind Figure 6)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFileSpectrum file name in subdirectory "sp"meta.id;meta.filecharInstInstrument ("SPRAT", "LRIS", "MODS" or "SNIFS")meta.id;instrcharMJD[59043/59312.6] Modified Julian Date of observationdtime.epochfloatspInteractive spectrum plotmeta.ref.urlchar