TITLE: GCN CIRCULAR NUMBER: 44946 SUBJECT: GRB 260610B: Terskol optical observations DATE: 26/06/15 08:46:27 GMT FROM: Nicolai Pankov at IKI <colinsergesen@gmail.com> N. Pankov (IKI), A. Salakhotdinova (INASAN), A. Shein (INASAN), E. Postnikova (INASAN), A. Pozanenko (IKI), A. Moskvitin (SAO RAS), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260610B (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-2000 2-meter telescope of the Terskol Observatory on epochs 2026-06-11 and 2026-06-12. The R-band observations were carried out using the CCD-photometer. In the first epoch we acquired a series of 3x120+12x120 sec images, while in the latter epoch 9x120 sec images were obtained. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek & Perley, GCN 44932) is clearly detected in our co-add images. The observational properties and preliminary photometry are provided further: Date UTstart t-T0 Exp. Filter Mag Err UL (mid,d) (n*s) (3-sigma) 2026-06-11 21:33:51 1.48481 3x120+12x90 R 19.81 0.06 22.4 2026-06-12 19:46:19 2.40802 9x120 R 20.70 0.13 22.3 The photometry is based on nearby SDSS stars (R-magnitudes obtained via Lupton 2005 transformation equations; Moskvitin et al., GCN 44918) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44946. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...