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GCN Circular 32898

GRB 221028A: 1.3m DFOT Optical upper limit
2022-10-31T07:20:02Z (2 years ago)
Amit Kumar Ror at ARIES <>
Amit Kumar Ror, Snehlata, Rahul Gupta, S. B. Pandey, Amar Aryan, Ankur
Ghosh, Dimple, and Kuntal Misra (ARIES) report:

We observed Swift-BAT detected GRB 221028A (Lien et al. GCN 32874) using
the 2Kx2K CCD Imager mounted on the 1.3m Devasthal Fast Optical Telescope
(DFOT) located at the Devasthal observatory of Aryabhatta Research
Institute of Observational Sciences (ARIES), India. The observations were
started on 2022-10-28 at 15:17:46, i.e., around 2 hours after the BAT
trigger. We have taken multiple frames, each having an exposure time of 300
sec in the R filter. We did not detect any new source within the XRT error
circle 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


2022-10-28 15:17:46    ~2        R        300x6   > 21.5

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.

The non-detection of the optical afterglow is consistent with Kumar et al.
GCNs 32876, 32886; Hu et al. GCN 32878; Lipunov et al. GCN 32879;
Strausbaugh et al. GCN 32881; Niwano et al. GCN 32883; Watson et al. GCN
no. 32888; Belkin et al. GCN 32889; Odeh GCN 32894; and Komesh et al. GCN

This circular may be cited.
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