TITLE:   GCN CIRCULAR
NUMBER:  43773
SUBJECT: EP260210a: Mondy optical upper limits
DATE:    26/02/17 15:04:00 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:

We observed the field of the fast X-ray transient EP260210a (Shi et al. GCN 43681) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 10 and 14 taking several 120-seconds frames in the R band. In the refined EP-FXT error circle (Yang et al., GCN 43696) we do not detect any new optical source in the stacked frames of our data. All catalogued sources located inside the refined EP-FXT error circle are detected in our stacked frames and do not exhibit any significant variations between the two epochs. In particular, the only one galaxy is presented within the refined EP-FXT error circle at coordinates of (J2000) 11:19:19.81 +45:23:43.8 in the SDSS catalogue.
Preliminary photometry of the galaxy and observational details are the following:

Date        UT start  t-T0      Exp.    Filter SDSS_galaxy   UL      Site/Telescope
                     (mid,days) (n*s)                       (3sigma)
2026-02-10  15:18:13  0.22584   30*120  R      20.29+/-0.05  22.7    Mondy/AZT-33IK
2026-02-14  20:08:59  4.42816   30*120  R      20.31+/-0.06  22.4    Mondy/AZT-33IK

The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction.
Our results are consistent with other published observations (Kang et al., GCN 43683; Fortin et al., GCN 43684; Li et al., GCN 43687; Aryan et al., GCN 43692; Lipunov et al., GCN 43697).