TITLE: GCN CIRCULAR NUMBER: 31844 SUBJECT: GRB 220403B: Mondy optical upper limit DATE: 22/04/06 16:37:01 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP), S. Belkin (IKI) report on behalf of GRB IKI FuN: We observed the field of GRB 220403B (Klingler et al., GCN 31820) with AZT-33 telescope of Mondy observatory starting on April, 05 (UT) 15:00:54. We do not detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Rossi et al., GCN 31826; Pankov et al., GCN 31837; Hu et al., GCN 31841; see also early upper limits in Lipunov et al., GCN 31825; Grossan et al., GCN 31830) in the combined image. Preliminary photometry of the combined image is following Date, UT start, t-T0, Exp., Filter, OT, Err, UL(3 sigma) (mid, days) 2022-04-05 15:00:54 1.77723 20*120 R n/d n/d 23.2 The photometry is based on nearby USNO-B1.0 stars, R2 magnitude USNO-B1.0_id R2 1791-0003982 16.77 1791-0003984 17.83