TITLE: GCN CIRCULAR NUMBER: 42476 SUBJECT: GRB 251026A: Mondy optical upper limit DATE: 25/10/27 13:34:08 GMT FROM: Alina Volnova at IKI RAS <alinusss@gmail.com> A. Volnova (IKI), A. Pozanenko (IKI) , N. Pankov (HSE, IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We observed the field of GRB 251026A detected by SVOM/ECLAIRs (Cao et al., GCN 42454) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting Oct. 26, 2025, 20:15:58 (UT) taking several frames with 120 s exposures. Inside the error box of the SVOM/MXT (Cao et al., GCN 42454) we did not detect any new uncatalogued source. Photometry and observational details are the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-26 20:15:58 0.51293 30*120 R n/d n/d 22.4 The photometry is based on several nearby PS1 stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42476. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...