TITLE: GCN CIRCULAR NUMBER: 44877 SUBJECT: GRB 260604C: further SAO RAS optical observations DATE: 26/06/08 22:27:43 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of long GRB 260604C discovered by Fermi (The Fermi GBM team, GCN 44822; Neights & Meegan, GCN 44831); SVOM (Gotz et al., GCN 44823) and GECAM-B (Luo et al., GCN 44854) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. We obtained 12 x 300 sec. images in Rc band on June 08, 20:01:14--21:07:58 UT. The OT (Lipunov, GCN 44827; Konno et al., GCN 44828; GCN 44836; Zhu et al., GCN 44832; Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843; Chen et al., GCN 44851; Moskvitin et al., GCN 44852; Sasaki et al., GCN 44857; Pankov et al., GCN 44858; Pankov et al., GCN 44862; Burkhonov et al., GCN 44865; Lincetto et al., GCN 44873) is detected in our stacked image with the following brightness: Date UTstart t-T0 Exp. Filter Mag +/- Err. UL (mid,d) (n*s) (3-sigma) 2026.06.08 20:01:14 4.01102 12*300 Rc 23.08 +/- 0.18 23.8 The preliminary photometry is based on nearby SDSS stars (R-magnitudes were obtained using Lupton 2005 transformation equations) as in Moskvitin et al., GCN 44852, and was not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...