TITLE: GCN CIRCULAR NUMBER: 39496 SUBJECT: EP250223a: CrAO ZTSH optical observation DATE: 25/02/26 17:18:16 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com> E. Mazaeva (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), N. Pankov (HSE, IKI), A. Volnova (IKI) report on behalf of IKI GRB-FuN collaboration: We observed the field of EP250223a (Lian et al., GCN 39429) 2.6-meter ZTSh telescope of CrAO starting on (UT) 2025-02-25 18:01:15. The optical counterpart of EP250223a (Hauptmann et al., GCN 39436; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Ducoin et al., GCN 39453; O’Neill et al., GCN 39455; Aryan et al., GCN 39464; Saikia et al., GCN 39472; Wang et al., GCN 39476) at the redshift of 2.756 (Levan et al., GCN 39438) is clearly detected. The preliminary photometry of the optical counterpart is the following: Date UT start T-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2025-02-25 18:01:15 2.15250 41x120 R 20.62 0.05 22.2 The magnitudes were calibrated using nearby PS1 stars using Lupton transformations to R-magnitude. No correction has been made for a Galactic extinction towards the counterpart. View this GCN Circular online at https://gcn.nasa.gov/circulars/39496. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...