GCN 44173: EP260329b: Mondy and Assy-Turgen optical upper limits

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

We observed the field of the fast X-ray transient EP260329b (Song et al.,
GCN 44142; EP Team, GCN 44155) with the AZT-33IK 1.5m telescope of the
Sayan Solar Observatory (Mondy) taking several 40-second expositions in
R-band, and with the AZT-20 telescope of Assy-Turgen observatory taking
several 30-second exposures in r' filter on Mar. 29. In the stacked frames
we do not detect the optical counterpart reported previously (Li et al.,
GCN 44139; Zhu et al., GCN 44140; Eyles-Ferris et al., GCN 44144; Aryan et
al., GCN 44147; Lipunov et al., GCN 44150; Mo et al., GCN 44163; O'Neill et
al., GCN 44169).
Preliminary photometry and observational details are the following:

Date        UT start  t-T0      Exp.    Filter Obj.   Err.  UL
 Site/Telescope
                     (mid,days) (n*s)                      (3sigma)
2026-03-29  15:24:19  0.22110   90*40   R      n/d    n/d   21.1
 Mondy/AZT-33IK
2026-03-29  19:57:04  0.40444   80*30   r      n/d    n/d   21.6
 Assy-Turgen/AZT-20

The photometry is based on several nearby stars from the SDSS-DR16
catalogue (Lupton transformations were used for the R-band values) and is
not corrected for the Galactic extinction.