GCN Circular 33934

Jada Vail, Maggie Li, Anna Ho (Cornell), Harsh Kumar, Vishwajeet Swain (IIT Bombay), Dmitry Svinkin (Ioffe Institute), Daniel Perley (LJMU):

We report the discovery of a fast-evolving red transient in Zwicky Transient Facility (ZTF) and GROWTH India Telescope (GIT) data.

ZTF23aamxeqf (AT2023jxk
Not found
 
 
) was discovered at the position (J2000) of:

RA = 17:02:36.97 (255.6540479 deg)

Dec = +51:52:05.09 (51.8680802 deg)

on 2023 June 5 by ZTF at g = 19.22 +/- 0.13 mag (MJD=60100.20252). ZTF also obtained a detection ~1.6 hours later at r = 18.96 +/- 0.11 mag (MJD=60100.26712). Forced photometry on P48 images revealed non-detections prior to discovery at g > 19.91 mag (MJD=60099.45061) and r > 20.14 mag (MJD=60099.40459), indicating a fast rise rate of >0.9 mag/day in g and >1.5 mag/day in r. Forced photometry also shows two detections later that night at g = 19.84 +/- 0.18 (MJD=60100.44324) and r = 19.14 +/- 0.08 (MJD=60100.42868), implying that the transient was red.

The fast rise and fall rates implied by ZTF photometry motivated us to trigger GIT for additional imaging. GIT imaging 1.5 days after the first ZTF detection showed a tentative (3-sigma) detection at  r = 22.4 +/- 0.2 mag, indicating an average fading rate of 2.3 mag/day in r-band.

The Galactic latitude of AT2023jxk
Not found
 
 
 is 37.6 degrees, and the Galactic reddening towards the direction of AT2023jxk
Not found
 
 
 is: E_(g-r) = 0.032 from Schlafly & Finkbeiner (2011). There is no counterpart within 3 arcseconds in either Legacy Survey DR9 imaging or PS1 imaging.

The fast rise, fast decay, red color, and lack of archival optical counterpart of AT2023jxk
Not found
 
 
 make it a strong candidate afterglow. However, we did not identify any GRBs coincident with this position during the time window between the last non-detection and the first detection: Konus-Wind was observing the whole sky during the entire interval of interest (except ~1 hour between 05:58:03 - 06:58:16 on June 4) and did not detect any counterpart.

Additional observations, including photometry and spectroscopy, are encouraged to determine the nature of this transient.  
 

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 operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.