AstroNote 2021-103

We report the discovery and classification of ZTF21aanxhjv/AT2021ehb, a young, UV-bright tidal disruption event (TDE) in a galaxy at z=0.017.  The nuclear transient was first detected by the Zwicky Transient Facility (ZTF; Bellm et al. 2019; Graham et al. 2019) NSF MSIP Northern Sky Survey on 2021 March 1 with g=19.1 mag, and first reported to TNS as a ZTF transient and early SN candidate by ALeRCE on 2021 March 3.  The source continued to rise to g=17.4 mag over 21 days, with a persistent blue color of g-r ~ = -0.5 mag.  We obtained an Palomar 60in SEDM low-resolution (R~100) spectrum on 2021 March 25 which measured a blue continuum and weak, broad features including broad Halpha and Hbeta lines.  The host galaxy redshift is determined from the GLADE v2.3 catalog, and is consistent with a template fit to the SEDM with a TDE spectrum using SNID (Blondin & Tonry 2007).  We triggered a Swift observation which was obtained on 2021 March 26 which detected a bright UV source with uvw2=16.59 +/- 0.04 mag.  The bright UV flux, with uvw2-r < -1 mag, persistent blue optical color, slow rise to peak, and blue continuum and broad line features are consistent with a TDE.  We do not detect any significant X-ray emission with the Swift/XRT, but we are continuing monitoring with a 2 day cadence. 

Further follow-up observations for this bright, nearby TDE still on the rise to peak, are encouraged.

                                                                                                                                                                           We thank the Swift team for the prompt approval and execution of our TOO observation.

This report is based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is a project led by PI S. R. Kulkarni at Caltech, and supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW. Alert distribution service provided by DIRAC@UW. Alert filtering is running in the GROWTH marshal system (Kasliwal et al. 2019), supported by NSF PIRE grant 1545949.