{
  "createdOn": 1742665570804,
  "body": "N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:\n\nWe performed optical observations of the field of EP250321a (Hu et. al, GCN 39800; Page et. al, GCN 39811, Hu et. al, GCN 39833) at the redshift of z = 4.368 (Zhu et. al, GCN 39769) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations started on (UT) 2025-03-21 16:42:58, i.e. about 0.46 days since trigger. The optical afterglow (Fu et. al, GCN 39804; Perez-Garcia et. al, GCN 39805; Brivio et. al, GCN 39807; Zhu et. al, GCN 39809; Becerra et. al, GCN 39810; Pérez-Fournon et. al, GCN 39812; Lee et. al, GCN 39815; Han et. al, GCN 39817; Jin et. al, GCN 39822; Zhu et. al, GCN 39827; Gill et. al, GCN 39831; Zheng et. al, GCN 39832) is detected in the stacked image. The preliminary photometry is as follows:\n\nDate       UT start  t-T0         Exp.    Filter OT     Err   UL(3sigma)\n                     (mid, days)  (s)            \n2025-03-21 16:42:58  0.46042      30*120  R      22.41  0.28  22.8\n\nThe photometry is based on nearby stars of SDSS-DR12 and has not been corrected for the Galactic extinction.\n\nSDSS-DR12\nRA Dec R(Lupton transformations, 2005)\n179.2552 +17.3825 18.123 +/- 0.049\n179.2436 +17.3713 18.846 +/- 0.012",
  "subject": "EP250321a: Mondy AZT-33IK Optical Observations",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>",
  "circularId": 39836,
  "editedOn": 1742759384256,
  "format": "text/plain",
  "bibcode": "2025GCN.39836....1P",
  "eventId": "EP250321a",
  "submitter": "Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>",
  "version": 2,
  "submittedHow": "web"
}