{
  "body": "A. Volnova (IKI), I. Sokolov (INASAN), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of IKI GRB-FuN:\n\nWe 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.\nPreliminary photometry and observational details are the following:\n\nDate        UT start  t-T0      Exp.    Filter Obj. Err.  UL      Site/Telescope\n                     (mid,days) (n*s)                    (3sigma)\n2026-04-25  20:02:10  9.63709   20*180  R      n/d  n/d   22.5    Terskol/Zeiss-2000\n2026-04-26  15:50:09  10.45948  40*120  R      n/d  n/d   22.9    Mondy/AZT-33IK\n\nThe photometry is based on nearby USNO-B1.0 stars (R2-magnitudes) and is not corrected for Galactic extinction.",
  "format": "text/plain",
  "submittedHow": "web",
  "eventId": "EP260416a",
  "submitter": "Alina Volnova at IKI RAS <alinusss@gmail.com>",
  "bibcode": "2026GCN.44419....1V",
  "createdOn": 1777451358121,
  "subject": "EP260416a: Mondy and Terskol optical upper limits",
  "circularId": 44419
}