TITLE: GCN CIRCULAR NUMBER: 44977 SUBJECT: GRB 260610B: AbAO optical observations DATE: 26/06/18 10:47:10 GMT FROM: Nicolai Pankov at IKI <colinsergesen@gmail.com> N. Pankov (IKI), R. Ya. Inasaridze (AbAO), A. Moskvitin (SAO RAS), V. Aivazyan (AbAO), A. Pozanenko (IKI), 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 AS-32 70-cm telescope of the Abastumani Astrophysical Observatory (AbAO). We acquired a series of 98x60 sec images in the R-band using a CCD-photometer, starting on 2026-06-12 20:18 UT (i.e. 1.856 days since trigger). 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; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959; Moskvitin et al., GCN 44963) is detected in the co-add image of 96x60 sec. The observational properties and preliminary photometry are provided further: Date UTstart t-T0 Exp. Filter Mag Err UL (mid,d) (n*s) (3-sigma) 2026-06-12 20:18:50 1.88931 96x60 R 20.59 0.10 22.0 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/44977. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...