TITLE: GCN CIRCULAR NUMBER: 45251 SUBJECT: GRB 260727A: AbAO and SAO RAS optical observations DATE: 26/07/29 11:19:50 GMT FROM: Nicolai Pankov at IKI <colinsergesen@gmail.com> N. Pankov (IKI), A. Moskvitin (SAO RAS), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), M. Zhuzhunadze (AbAO) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 260727A (Li et al., GCN 45220; Harsha. et al., GCN 45225; Cheung et al., GCN 45233; Li et al., GCN 45236; Svinkin et al., GCN 45242; Wang et al., GCN 45247) with the 0.7m AS-32 telescope of Abastumani Observatory (AbAO) and the Zeiss-1000 1m telescope of the Special Astrophysical Observatory of the RAS (SAO RAS). The observations started on 2026-07-27 at 19:15:15 UT (~0.81 days after the SVOM trigger) at AbAO. The series of 70x60 s exposures in the R-band was obtained using the CCD-photometer. The observations continued at SAO RAS starting 2026-07-28 at 00:12:38 UT (~ 1.0 days since trigger). The series of 6x300 s exposures was obtained in the Rc-band using the CCD-photometer. We performed catalog search and image subtraction (against the PS1 r-band template image) on co-add images from both observatories. The observational properties are provided further. Date UT start t-T0 Exp. Filter UL(3sigma) Site/Telescope (mid, days) (s) 2026-07-27 19:15:15 0.81092 69x60 R 20.9 AbAO/AS-32 2026-07-28 00:12:38 1.00509 6x300 Rc 22.9 SAO RAS/Zeiss-1000 No optical candidates were found in the EP-FXT error circle (Li et al., GCN 45236) up to limiting magnitude presented above. The field was also observed in optical by (Shi et al., GCN 45223; Freeberg et al., GCN 45224; Starling et al., GCN 45226; Lechapelain&Midavaine, GCN 45228; Mohan et al., GCN 45231; Bochenek et al., GCN 45240) but no candidate transients were reported. The photometry is based on nearby stars from USNO-B1.0. No correction has been made for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45251. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...