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.

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