AstroNote 2023-99

During the night of 2023 Apr 21 (UT), the Zwicky Transient Facility (ZTF) detected a new optical transient, internally designated ZTF23aagunkc, at the following position (J2000):

RA, Dec = 15:58:13.048 +08:54:24.98 (239.5543649 +8.9069399)

The transient was observed as part of the partnership survey and flagged by the ZTFReST project (Andreoni & Coughlin et al., 2021). The magnitude at the time of first detection (JD 2460055.89159) was r = 18.78 +/- 0.07 mag (all magnitudes AB, not corrected for Galactic extinction). An r-band detection ~2 days after the discovery (JD 2460057.93245) showed that the transient had faded by approximately half a magnitude (r = 19.21 +/- 0.15 mag). Non-detections in g > 20.3 mag and r > 20.4 mag at 2460053.9 (~2 days before discovery) suggest a rapid rise (~1.5 mags in 2 days).

The transient color was initially very blue on the date of discovery with g-r = -0.41 +/- 0.09 (g- and r-band images separated by 1.2 hours). On Apr 23rd night, the color became less blue with g-r = -0.2 +/- 0.2. The candidate is isolated and has no underlying source in PanSTARRS and Legacy Survey archival imaging. The candidate's Galactic elevation is b = 42 deg and extinction in the direction is low E(B-V)=0.04 mag.

Follow-up observations with 0.7m GROWTH-India Telescope (GIT) on 2460059.22727 confirm the fading and blue color of the transient with detections at r = 19.67 +/- 0.14 and g = 19.50 +/- 0.12. With the information at hand, we cannot exclude that the source is a Galactic CV, although the high Galactic latitude discourages this interpretation. Follow-up 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, and IN2P3, France. Operations are conducted by COO, IPAC, and UW. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the telescope’s operations. Telescope technical details are available at https://sites.google.com/view/growthindia/.