TITLE:   GCN CIRCULAR
NUMBER:  42950
SUBJECT: GRB 251122A/EP251122a: CrAO ZTSh optical observations
DATE:    25/12/02 15:21:45 GMT
FROM:    Alina Volnova at IKI RAS <alinusss@gmail.com>

A. A. Volnova (IKI), V. V. Rumyantsev (CrAO), A. S. Pozanenko (IKI), N. S. Pankov (IKI) report on behalf of IKI GRB-FuN collaboration:

We observed the FXT localization of GRB 251122A/EP251122a (Wang et al., GCN 42779; Lin et al., GCN 42800; Yin et al., GCN 42808; Wang et al., GCN 42809) with the ZTSH telescope of CrAO starting on 2025-11-11 (UT) 21:37:17 UT and taking several 120s exposures in R-band. The optical counterpart (Cheng et al., GCN 42803; Li et al., GCN 42806; Sun et al., GCN 42807; Ma et al., GCN 42811; Gupta et al., GCN 42813; Busmann et al., GCN 42814) is detected in the stacked frame. Preliminary photometry is the following:

Date        UT start  t-T0       Exp.    Filter  OT     Err.  UL      Site/Instrum
                     (mid,days)  (n*s)                       (3sigma)
2025-11-22  21:37:17  0.34097    20*120  R       22.36  0.25  22.8    CrAO/ZTSh

The photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.