TITLE:   GCN CIRCULAR
NUMBER:  43499
SUBJECT: EP260119a: Mondy and SAO RAS optical upper limits
DATE:    26/01/22 10:50:53 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

N. Pankov (IKI), A. Moskvitin (SAO RAS), A. Volnova (IKI), O. Spiridonova (SAO RAS), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of the IKI-GRB-FuN collaboration:

We observed the field of the EP260119a (Jiang et al., GCN 43447; GCN 43465; Cheng et al., GCN 43449) at the redshift of z ~ 5.47 (Corcoran et al., GCN 43469) using the AZT-33IK telescope of the Mondy observatory starting on 2026-01-20 (UT) 18:52:22 and 2026-01-21 (UT) 19:10:23, and the Zeiss-1000 of the SAO RAS starting on 2026-01-21 (UT) 03:05:44. 
In the stacked frame of each observational epoch we do not detect the optical source reported previously (Fortin et al., GCN 43450; GCN 43455; Eyles-Ferris et al., GCN 43452; Moskvitin and Spiridonova, GCN 43463; Liu et al., GCN 43464; Ma et al., GCN 43466; Zheng et al., GCN 43468; Corcoran et al., GCN 43469; Bochenek and Perley, GCN 43472; Pankov et al., GCN 43476; Jin et al., GCN 43496). Preliminary photometry and observation details are listed below:

Date        UT start  t-T0       Exp.    Filter Mag  MagErr.  UL       Site/Telescope
                     (mid,days)  (n*s)                       (3sigma)
2026-01-20  18:52:22  1.80804    45x120  I      n/d  n/d      22.3     Mondy/AZT-33IK
2026-01-21  03:05:44  2.13449    8*300   Ic     n/d  n/d      21.9     SAO RAS/Zeiss-1000
2026-01-21  19:10:23  2.82417    52*120  I      n/d  n/d      21.7     Mondy/AZT-33IK

Photometric data are based on nearby SDSS stars (I-magnitudes obtained using the 2005 Lupton transform) and not corrected for Galactic extinction.