AstroNote 2023-350

As part of the ZTF high-cadence experiment (Ahumada et al., 2023-349), we identified ZTF23abulqve/AT 2023aafe as a rapidly evolving transient.

AT2023aafe was first reported in the ZTF alert stream on 2023-Dec-15 8:41 UTC (MJD 60293.3621) at m_g=19.8 +/- 0.1 mag, and was notable for substantially brightening by 0.4 mag in g-band over the course of the night. The source was blue, with an approximate colour of g-r = 0.3 mag. Furthermore, forced photometry reveals a faint g-band pre-detection the previous night (2023-Dec-14 12:43 UTC,  MJD 60292.53) at 22.0 +/- 0.3 mag. The transient thus brightened by >2.4 mag in a day, peaking at m_g <19.4 +/- 0.1 mag, and has since been fading by >0.25 mag per day. 

We obtained a spectrum of AT2023aafe with DBSP at the Palomar 200-inch, but the SNR was insufficient to secure a classification. The spectrum reveals a blue continuum. Without secure emission lines, we cannot exclude a galactic origin for this transient, but note that it has a galactic latitude of b=27 degrees.

The transient appears to be hostless, with no underlying point source visible in PanSTARRS imaging.

We have requested Swift observations to search for a possible X-ray counterpart. Spectroscopic observations are strongly encouraged to confirm the nature of this transient.

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 Oskar Klein Center at Stockholm University, the University of Maryland, University of California, Berkeley , the University of Wisconsin at Milwaukee, University of Warwick, Ruhr University, Cornell University, Northwestern University and Drexel University. Operations are conducted by COO, IPAC, and UW. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski (Duev et al. 2019). Fritz and SkyPortal acknowledge the generous support of The Gordon and Betty Moore Foundation, through the Data-Driven Investigator Program.