J/ApJ/909/102ivo://CDS.VizieR/J/ApJ/909/102doi:10.26093/cds/vizier.19090102CDSBrightman M.Ward C.Stern D.Mooley K.De K.Gezari S.Van Velzen S.,Andreoni I.Graham M.Masci F.J.Riddle R.Zolkower J.2022-11-25T13:13:36Z2022-08-29T15:03:35ZCDS support team

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

cds-question@unistra.frx-ray-sourcesvisible-astronomyspectroscopygalaxiesWe present the discovery of a luminous X-ray transient, serendipitously detected by Swift's X-ray Telescope on 2020-February-5, located in the nucleus of the galaxy SDSSJ143359.16+400636.0 at z=0.099 (luminosity distance D_L_=456Mpc). The transient was observed to reach a peak luminosity of ~10^44^erg/s in the 0.3-10keV X-ray band, which was ~20 times more than the peak optical/UV luminosity. Optical, UV, and X-ray light curves from the Zwicky Transient Facility and Swift show a decline in flux from the source consistent with t^-5/3^, and observations with NuSTAR and Chandra show a soft X-ray spectrum with photon index {Gamma}=2.9+/-0.1. The X-ray/UV properties are inconsistent with well-known active galactic nucleus properties and have more in common with known X-ray tidal disruption events (TDEs), leading us to conclude that it was likely a TDE. The broadband spectral energy distribution can be described well by a disk blackbody model with an inner disk temperature of 7.3_-0.8_^+0.3^x10^5^K, with a large fraction (>40%) of the disk emission upscattered into the X-ray band. An optical spectrum taken with Keck/LRIS after the X-ray detection reveals LINER line ratios in the host galaxy, suggesting low-level accretion onto the supermassive black hole prior to the event, but no broad lines or other indications of a TDE were seen. The stellar velocity dispersion implies that the mass of the supermassive black hole powering the event is log(M_BH_/M_{sun}_)=7.41+/-0.41, and we estimate that at peak the Eddington fraction of this event was ~50%. This likely TDE was not identified by wide-field optical surveys or optical spectroscopy, indicating that more events like this would be missed without wide-field UV or X-ray surveys.2021ApJ...909..102Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/909/102CatalogResearchIsServedByTAP VizieR generic servicerelated-toIX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)I/345 : Gaia DR2 (Gaia Collaboration, 2018)V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)J/ApJS/132/37 : Spectroscopy of Southern warm IR galaxies (Kewley+, 2001)J/A+A/480/611 : XMM-Newton slew survey catalogue, XMMSL1 (Saxton+, 2008)J/MNRAS/397/1177 : Swift-XRT observations of GRBs (Evans+, 2009)J/A+A/512/A34 : XMM-COSMOS Type 1 AGNs (Lusso+, 2010)J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)J/A+A/588/A103 : 2nd ROSAT all-sky survey (2RXS) source cat. (Boller+, 2016)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/ApJ/819/154 : SDSS-DR7 QSOs with X-ray and UV luminosities (Lusso+, 2016)J/ApJS/233/17 : Swift/BAT AGN sp. survey. V. X-ray data (Ricci+, 2017)J/ApJ/883/111 : UV-Opt LCs of ASASSN-19bt detected by TESS (Holoien+, 2019)J/ApJ/872/198 : LCs of tidal disruption flare AT2018zr (van Velzen+, 2019)J/ApJ/902/86 : Type Ic SN 2020bvc UV to NIR LCs & opt. spectra (Ho+, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/909/102https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/909/102http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/909/102https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/909/102https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/909/102http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/909/102GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapX-rayOpticaldefaultJ/ApJ/909/102/fig5Keck/LRIS spectrum of the nucleus of SDSS J143359.16+400636.0 taken on 2020-February-18, 13d after the X-ray transient was detected by SwiftrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambda[3066.4/10303] Wavelength; in Angstrom units0.1nmem.wldoubleFlux[-6.02e-17/1.6e-16]? Observed flux; in erg/cm^2^/s/{AA} unitscW.m**-2.nm**-1meta.unitdoublenullablee_Flux[8e-19/6.5e-17] Uncertainty in FluxcW.m**-2.nm**-1stat.error;phot.fluxdouble