GCN Circular 44419
Subject
EP260416a: Mondy and Terskol optical upper limits
Event
Date
2026-04-29T08:29:18Z (10 days ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), I. Sokolov (INASAN), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of IKI GRB-FuN:
We observed the field of the fast X-ray transient EP260416a (Hu et al., GCN 44307, 44324) at z = 1.909 (He et al., GCN 44336; An et al., GCN 44339) in R band with the Zeiss-2000 telescope of the Terskol observatory starting on 2026-04-25 (UT) 20:02:10 and with the AZT-33IK telescope of the Mondy observatory starting on 2026-04-26 (UT) 15:50:09. The optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334; He et al., GCN 44336; An et al., GCN 44339; Jelinek et al., GCN 44341; Guziy et al., GCN 44351; Ho et al., GCN 44354; Pawar et al., GCN 44373; Li et al., GCN 44376; Moskvitin et al., GCN 44395; Volnova et al., GCN 44398) is not detected in the stacked frames of every epoch.
Preliminary photometry and observational details are the following:
Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope
(mid,days) (n*s) (3sigma)
2026-04-25 20:02:10 9.63709 20*180 R n/d n/d 22.5 Terskol/Zeiss-2000
2026-04-26 15:50:09 10.45948 40*120 R n/d n/d 22.9 Mondy/AZT-33IK
The photometry is based on nearby USNO-B1.0 stars (R2-magnitudes) and is not corrected for Galactic extinction.