TITLE: GCN CIRCULAR NUMBER: 31619 SUBJECT: ZTF22aabjpxh/AT2022cva: ZTF Discovery of a Rapidly Fading Transient with a Likely Long-GRB Counterpart DATE: 22/02/21 04:13:18 GMT FROM: Anna Ho at UC Berkeley Anna Y. Q. Ho (UCB), Daniel Perley (LJMU), Igor Andreoni (JSI), Mansi Kasliwal (Caltech), Dmitry Svinkin (Ioffe Institute), Aaron Tohuvavohu (U. Toronto), Harsh Kumar (IITB) on behalf of the Zwicky Transient Facility (ZTF) collaboration: We report the discovery of ZTF22aabjpxh (AT2022cva), a rapidly fading red transient located at 16:03:39.35 +31:14:04.72 (J2000) 240.9139656, 31.2346451 (J2000) first detected as part of the ZTF partnership survey. The source was discovered on JD 2459630.0001 at r=16.59 ± 0.01 mag, which was 0.98 days after the last non-detection (r>19.34). The transient position is 2'' from a galaxy in SDSS with a photometric redshift of 0.25 ± 0.05. Due to the rapid rise of almost 3 magnitudes in one day, and the possible high luminosity, we triggered follow-up photometry with the Spectral Energy Distribution Machine (SEDM) on the 60-inch telescope at Palomar Observatory (P60). SEDM photometry obtained the night after discovery established a rapid fade rate of 2.25 magnitudes in 0.88 days as well as red colors (g-r=0.41 ± 0.08, corrected for Galactic extinction). The transient was also detected as part of the ZTF public survey that night, and the rapid fade triggered the ZTFReST pipeline (Andreoni & Coughlin et al. 2021). Konus-Wind detected a long-duration GRB at UT 2022-02-19 09:27:25.350 that is consistent with the position of AT2022cva. The GRB burst time is 2.5 hours before the first ZTF detection. The GRB was also weakly detected by BAT. The ZTF optical position was outside the coded BAT FoV at the time of the burst, and the observed counts are consistent with a relatively soft burst coming from outside the BAT field of view. The Konus-BAT IPN annulus is consistent with the position of the ZTF transient, and the association is highly likely. We conclude that AT2022cva is the likely afterglow to the Konus-Wind GRB. Given the possible low redshift (z~0.3) continued photometric and spectroscopic observations are encouraged. 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 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, IN2P3, University of Warwick, Ruhr University Bochum and Northwestern University. Operations are conducted by COO, IPAC, and UW. -- Anna Ho