TITLE: GCN CIRCULAR NUMBER: 31869 SUBJECT: GRB 220403B: 1.3m DFOT Optical upper limit DATE: 22/04/10 12:39:32 GMT FROM: Rahul Gupta at ARIES, India Amit Kumar Ror, Rahul Gupta, Amit Kumar, Dimple, Ankur Ghosh, Amar Aryan, Brajesh Kumar, S. B. Pandey, and Kuntal Misra (ARIES) report: We observed the Swift-BAT and Fermi-GBM detected GRB 220403B (Klingler et al., GCN 31820; Hamburg et al., GCN 31829) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at Devasthal observatory of Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2022-04-04 at ~ 17:32 UT, i.e., ~ 20.82 hours after the BAT trigger. We have taken multiple frames having an exposure time of 300 sec in the R filter. We stacked the images after the alignment. We did not detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Lipunov et al., GCN 31825; Rossi GCN 31826; Pankov et al., GCN 31837; and Hu et al., GCN 31841) in our stacked image. We obtain the following 3-sigma upper limit in the stacked image. Date Start_UT T_start-T0 (hours) Filter Exp time (sec) Limiting magnitude ============================================================= 2022-04-04 17:32:01 ~20.82 R 300 sec*24 > 21.6 The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited.