TITLE: GCN CIRCULAR NUMBER: 39540 SUBJECT: GRB 250226A: KAO Optical Upper Limit DATE: 25/02/28 20:48:07 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com> N. Pankov (HSE, IKI), A. M. Abdelaziz (NRIAG), M. Abdelkareem (NRIAG), E. Amin (NRIAG), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We performed optical observations of the field of GRB 250226A (The Fermi GBM team, GCN 39479; V.Lipunov et. al, GCN 39481; Jiang et. al, GCN 39482; An et. al, GCN 39486; Zhu et. al, GCN 39487; Magnani et. al, GCN 39488; Li et. al, GCN 39489; Li et. al, GCN 39492; Aryan et. al, GCN 39509; Zou et. al, GCN 39511; Jiang et. al, GCN 39513; Li et. al, GCN 39514; Junjie-Jin et. al, GCN 39515; Thakur et. al, GCN 39518; Poidevin et. al, GCN 39524; Pathak et. al, GCN 39530; Pankov et. al, GCN 39539) in the R filter with the 1.88-meter telescope of the Kottamia Astronomical Observatory (KAO). The observations started on (UT) 2025-02-28 00:30:36, i.e. ~1.78 days since trigger and consists of 39x150 sec exposures. We do not detect the optical counterpart in the stacked image. The preliminary upper limit is as follows: Date UT start t-T0 Exp. Filter UL(3sigma) (mid, days) (s) 2025-02-28 00:30:36 1.78084 39*150 R 22.3 The photometry is based on nearby stars from the USNO-B1.0 catalog and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39540. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...