TITLE: GCN CIRCULAR NUMBER: 39424 SUBJECT: GRB 250221A: Mondy optical observations DATE: 25/02/22 12:25:53 GMT FROM: Alexei Pozanenko at IKI, Moscow grb.alex@gmail.com

N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunlo (ISTP), A. Volnova (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; Pankov et al., GCN 39422) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-33IK telescope of Mondy observatory starting on 2025-02-21 (UT) 12:25:52 in R filter.

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

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

2025-02-21 12:25:52 0.38490 23x60 R 20.30 0.05 22.5

The photometry is based on nearby USNO-B1.0 (R2) stars.

View this GCN Circular online at https://gcn.nasa.gov/circulars/39424. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...