TITLE: GCN CIRCULAR NUMBER: 39422 SUBJECT: GRB 250221A: Assy optical observations DATE: 25/02/22 11:10:50 GMT FROM: Alexei Pozanenko at IKI, Moscow grb.alex@gmail.com

N. Pankov (HSE, IKI), V. Kim (FAI), M. Krugov (FAI), Y. Aimuratov (FAI), A. Volnova(IKI), A. Pozanenko (IKI) report on behalf of IKI GRB FuN:

We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-20 telescope of Assy-Turgen observatory starting on 2025-02-21 (UT) 15:25:09.55 in r' filter.

The afterglow is clearly detected. Preliminary photometry of the OT in the stacked image is the following

Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)

2025-02-21 15:25:09 0.50385 30x60 r' 20.90 0.05 22.8

The photometry is based on nearby PS1 stars.

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