TITLE: GCN CIRCULAR NUMBER: 45252 SUBJECT: EP260727a: SAO RAS optical observations DATE: 26/07/29 12:55:38 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> A. Moskvitin (SAO RAS), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of EP260727a (Hu et al., GCN 45235) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. We obtained 9*20 + 4*300 sec. images with Rc filter from 2026-07-27T23:31:14 to 2026-07-28T00:07:51 under mediocre weather conditions and seeing of 3".3. The OT (He et al., GCN 45234; Eyles-Ferris et al., GCN 45239; Adami et al., GCN 45243; Guziy et al., GCN 45245; also consistent with the EP-FXT position, Wu et al., GCN 45244) is clearly detected in the stacked image with the following brightness. Date UTstart t-T0 Exp. Filter Mag Err. UL (mid, h) (n*s) (3-sigma) 2026-07-27 23:31:14 3.1932 1380 Rc 21.64 +/- 0.17 22.5 Near the position of the second candidate proposed by Adami et al., (GCN 45243) we note the presence of an extended source with the coordinates (J2000.0) R. A. = 23:05:48.72; Dec. = +03:15:23.5 and brightness of R = 21.55 +/- 0.11. This preliminary photometry was given in the Vega system, calibrated against nearby SDSS stars (magnitudes converted with Lupton 2005 equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45252. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...