{
  "body": "A. Volnova (IKI), A. Pozanenko (IKI) , N. Pankov (HSE, IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:\n\nWe observed the field of the GRB 251023B / EP251023b (Kang et al., GCN Circ. 42392; Nakahira et al., GCN Circ. 42402; Wu et al., GCN Circ. 42415; Cheung et al., GCN Circ. 42407) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting Oct. 25, 2025, 17:50:36 UT, and taking several frames with 120 s exposures. The optical candidate reported by Mandarakas et al. (GCN Circ. 42404) is not detected in the stacked frame. Photometry and observational details are the following:\n\nDate        UT start  t-T0       Exp.    Filter  OT     Err.  UL\n                     (mid,days)  (n*s)                       (3sigma)\n2025-10-25  17:50:36  2.40386    40*120  R       n/d    n/d   22.7\n\nThe photometry is based on several nearby SDSS stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction.",
  "createdOn": 1761572669814,
  "subject": "GRB 251023B / EP251023b: Mondy optical upper limit",
  "circularId": 42478,
  "eventId": "GRB 251023B",
  "submittedHow": "web",
  "submitter": "Alina Volnova at IKI RAS <alinusss@gmail.com>",
  "bibcode": "2025GCN.42478....1V",
  "format": "text/plain"
}