TITLE: GCN CIRCULAR NUMBER: 43378 SUBJECT: GRB 251230A: Mondy Optical Observations DATE: 26/01/12 15:10:09 GMT FROM: Alina Volnova at IKI RAS <alinusss@gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 251230A (Lanava et al., GCN 43252; Wang et. al, GCN 43259; Osborne et. al, GCN 43263; Wang et. al, GCN 43272; Sbarrato et al., GCN 43275; Guo et. al, GCN 43299; Guo et. al, GCN 43301) in the R filter with the AZT-33IK 1.5-meter telescope of the Sayan Solar Observatory (SSO Mondy). The observations began on 2025-12-30 19:36:42 UT, i.e. ~0.77 days since trigger. The optical counterpart (Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; He et al., GCN 43269; Breeveld et. al, GCN 43271; He et al., GCN 43280; Antier et. al, GCN 43281; Ma et al., GCN 43282; Chatterjee et. al, GCN 43321) is not detected in the co-add image. The preliminary photometry and observation details are provided below: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (s) (3sigma) 2025-12-30 19:36:42 0.77001 15*120 R n/d n/d 20.4 The photometry was calibrated using nearby stars from USNO-B1.0 and is not corrected for the Galactic extinction. The obtained results do not contradict the measurements reported by other teams, including upper limits (Starling et. al, GCN 43267; Tak et al., GCN 43270; Gupta et. al, GCN 43277; Sankar et al., GCN 43279). View this GCN Circular online at https://gcn.nasa.gov/circulars/43378. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...