AstroNote 2026-176

AT2026obc is a rapidly rising blue transient located at (J2000):

01:07:49.425 +41:59:43.38

16.9559363 +41.9953843

The source was detected by the Zwicky Transient Facility (ZTF) as ZTF26aayznam, on 2026 May 31 11:26:58 (UT) at r=15.65 +/- 0.01 mag (alert forced photometry), and reported to the Transient Name Server (Sollerman et al., TNS Report No. 306824). The transient then brightened by 0.8 mag in r-band over the following 2 days. The color in the most recent observation is blue, g-r = -0.35 mag corrected for Milky Way extinction. 

The transient is coincident with a galaxy catalogued as V Zw 051. From NED the galaxy’s spectroscopic redshift is z=0.0374 +/- 0.0007 (Huchra et al. 1999). If located in the galaxy, the implied absolute magnitude would be M = -21.3 mag. 

A foreground CV cannot be excluded. We encourage follow-up observations to determine if this fast-rising blue transient is extragalactic. 

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 Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.