AstroNote 2023-297

We report observations of a quickly-evolving blue transient with a host-galaxy counterpart, AT2023vth (ZTF23ableqsp).

AT2023vth was discovered at a position (J2000) of:

which corresponds to a galactic latitude of 16 degrees.

The first ZTF detection was at r = 20.06 +/- 0.23 mag on 2023-10-16 03:05:41 UTC (MJD 60233.12895).  The next detection was at r = 17.95 +- 0.07 mag on 2023-10-18 02:46:59 UTC (MJD 60235.11596), implying a fast rise rate of 1 mag/day in r-band.

The transient reached a peak magnitude of g=17.56 +/- 0.05 mag on 2023-10-20 03:08:39 UTC (MJD 60237.63101)  From Schlafly & Finkbeiner (2011), the extinction at this location is E_(g-r) = 0.22.  The implied g-r color at peak light was g-r = -0.37 +- 0.09 mag.

During the transient’s fade, ZTF forced photometry revealed a fade rate of at least 0.25 mag/day in both r-band and g-band.

There is a clear galaxy counterpart in PanSTARRS 1.23 arcseconds away from AT2023vth with a photometric redshift of 0.13+/-0.02 (Beck et al. 2021, MNRAS, 500, 1633).  This would give a peak absolute magnitude of about -21.5.

Due to its fast rise, fast fade, blue color, and presence of a host-galaxy counterpart, we encourage spectroscopic follow-up observations to measure the redshift. The apparent magnitude as of a few days ago was r~21 mag (from ZTF forced photometry). 

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.