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.