TITLE: GCN CIRCULAR NUMBER: 43666 SUBJECT: GRB 260208A: Mondy optical observations DATE: 26/02/09 11:57:27 GMT FROM: Alina Volnova at IKI RAS <alinusss@gmail.com> A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 8 starting at 20:54:02 UT and taking several 120-seconds frames in the R band. The optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al.,GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665) is detected in the single frame. Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-02-08 20:54:02 0.66429 10*120 R 19.92 0.06 21.8 Mondy/AZT-33IK 2026-02-08 21:14:03 0.67819 10*120 R 20.14 0.07 21.8 Mondy/AZT-33IK 2026-02-08 21:34:04 0.69139 10*120 R 20.05 0.06 21.8 Mondy/AZT-33IK The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43666. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...