AstroNote 2023-57

During the night of 2023 March 13 (UT), the Zwicky Transient Facility (ZTF) detected a new optical transient, internally designated ZTF23aadaxfn, at the following position (J2000):

RA, Dec = 11:11:39.22 +55:40:29.1 (167.913436 +55.674739)

The transient was observed as part of the partnership survey and flagged by a filter designed to identify rapidly evolving transients. The magnitude at the time of first detection (JD 2460016.7873) was r = 19.47 +/- 0.15 mag (all magnitudes AB, not corrected for Galactic extinction). An r-band detection the following night (JD 2460017.8694) showed that the transient had brightened by one magnitude (r = 18.50 +/- 0.12 mag). We saved the source to the TNS and it was assigned the name AT2023dbc. 

The transient color is red: the color the night of March 14 is g-r = 2.06 +/- 0.31 (g and r images separated by 4 hours). The position is coincident with the catalogued galaxy NGC 3556 (Messier 108) at 10 Mpc, which implies an absolute magnitude of r = -10.5 mag at discovery absent any dust correction.  Given the edge-on morphology of the host galaxy and the red color of the transient, host extinction is likely substantial and the true luminosity may be significantly higher.

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.