TITLE: GCN CIRCULAR NUMBER: 31590 SUBJECT: ZTF22aaajecp/AT2022cmc: Zwicky Transient Facility discovery of a fast and red optical transient DATE: 22/02/14 18:47:06 GMT FROM: Igor Andreoni at JSI Igor Andreoni (JSI), Michael Coughlin (UMN), Tomas Ahumada (UMD), Mansi Kasliwal (Caltech), Daniel Perley (LJMU), Eric Burns (LSU), Mattia Bulla (OKC), Brad Cenko (NASA/GSFC), Shreya Anand (Caltech), Erik Kool (OKC) We report the discovery of the fast and red optical transient ZTF22aaajecp/AT2022cmc with the Zwicky Transient Facility (ZTF, Bellm et al. 2019, Graham et al. 2019) at coordinates: RA = 13:34:43.20 (203.6800149d) Dec = +33:13:00.44 (33.2167887d) ZTF22aaajecp was first detected on 2022-02-11 10:42 UT at r=20.73 +- 0.3 mag. The last ZTF upper limit before the first detection was measured on 2022-01-21 09:54 UT. ZTF22aaajecp increased its luminosity to r=19.04 +- 0.16 mag in 23.2 hours, then it faded by 0.8 mag in the following 48 hours. The latest detection of ZTF22aaajecp occurred on 2022-02-14 09:40 UT, r=19.84 +- 0.19 mag. The color of ZTF22aaajecp appears to be red, with g-r~0.25 mag and g-i~0.5 mag at the observed peak on 2022-02-12. The Galactic extinction on the line of sight is small, with E(B-V)=0.01 mag (Planck Collaboration et al., 2014). The source is located at a high Galactic latitude of b=78.85 deg. ZTF22aaajecp does not have any cataloged underlying source in deep Legacy Survey DR9 images. The fast evolution and red color suggest that ZTF22aaajecp could be a gamma-ray burst afterglow, but a spectroscopic confirmation is required to determine the nature of the transient. ZTF22aaajecp is spatially and temporally consistent with the Fermi-GBM short GRB 220211A (GBM trigger 666234473); however, it is located several degrees outside the IPN localization region for this event (Ridnaia et al. 2022; GCN 31584). Follow-up observations are strongly encouraged. ZTF22aaajecp was discovered by the ''ZTF Realtime Search and Triggering'' project (ZTFReST; Andreoni & Coughlin et al., 2021) within the ZTF Collaboration. 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, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.