TITLE:   GCN CIRCULAR
NUMBER:  38673
SUBJECT: EP241223a: Mondy AZT-33IK optical observations
DATE:    24/12/26 15:07:02 GMT
FROM:    Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>

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

We performed optical observations of the field of EP241223a (Zhou et. al, GCN 38660; Lipunov et. al, GCN 38661; Jin et. al, GCN 38665) in the R filter with the 1.5-meter AZT-33IK telescope of Sayan (Mondy) observatory. The observations began on 2024-12-24 14:16 UT, i.e. ~1.3 days since trigger. After the PS1 template subtraction, we do not find any new optical sources in the stacked image of 30*120 sec. The preliminary upper limit is as follows:

Date       UTstart   t-T0         Exp.    Filter  OT   Err.  UL(3sigma)
                     (mid, days)  (s)
2024-12-24 14:16:07  1.30885      30*120  R       n/d  n/d   21.8 

The photometry is calibrated using nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction.