TITLE: GCN CIRCULAR NUMBER: 41934 SUBJECT: GRB 250916A: SAO RAS Zeiss-1000 optical observations DATE: 25/09/22 09:39:39 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> A. Moskvitin, O. Spiridonova (SAO), N. Pankov (HSE), A. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Tao An and Yuanqi Liu (Shanghai Astronomical Observatory) report on behalf of GRB follow-up collaboration and IKI-GRB-FuN. We observed the field of the GRB 250916A (Fermi GBM team, GCN 41839; Arya et al., GCN 41843; Cheung et al., GCN 41855; Osborne et al., GCN 41862; Waratkar and Grefenstette, GCN 41871; Godwin and Meegan, GCN 41876) with the 1-m SAO RAS telescope Zeiss-1000 equipped with the CCD-photometer. We obtained 9 x 300 sec. images Rc band on September 21, 23:36:57 -- September 22, 00:47:22 UT (t_mid - T0 = 5.44639 days). The optical transient (Belkin et al., GCN 41847; Mohan et al., GCN 41858; Moskvitin et al., GCN 41859; Burkhonov et al., GCN 41860; de Ugarte Postigo et al., GCN 41863; Moskvitin et al., GCN 41870; Zheng and Filippenko, GCN 41873; Pankov et al., GCN 41892; Hall et al., GCN 41921) is clearly detected in the stacked frame with the brightness of R = 22.6 +/- 0.1. Date UT start t-T0 Exp. Filter OT Err. UL (3sigma) (mid, d) (s) 2025.09.21 23:36:57 5.44639 9 x 300 Rc 22.6 +/- 0.1 23.3 Preliminary photometry is based on the nearby objects from PanSTARRS (magnitudes converted with Lupton 2005 equations) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41934. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...