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GCN Circular 31869

GRB 220403B: 1.3m DFOT Optical upper limit
2022-04-10T12:39:32Z (2 years ago)
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

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.

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