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GCN Circular 35302

GRB 231205B: 1.3m DFOT Optical upper limit
2023-12-07T13:20:11Z (8 months ago)
Amit Kumar Ror at ARIES <>
Amit K. Ror, Rahul Gupta, Amar Aryan, and Shashi B. Pandey (ARIES) report:

We observed the field of GRB 231205B detected by Swift (Evans et al. 2023,
GCN 35269) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located
at the Devasthal Observatory of the Aryabhatta Research Institute of
Observational Sciences (ARIES), India. The observations were started on
2023-12-06 at 13:19:13 UT, i.e., ~ 0.86 days after the BAT trigger. We have
taken multiple frames with an exposure time of 300 s in the R filter. We
stacked the images after the alignment. We did not detect optical afterglow
in our stacked image within the enhanced Swift-XRT observation error box
(Osborne et al., 2023, GCN 35275). We obtain the following preliminary
3-sigma upper limit in the stacked image:

Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Limiting magnitude
2023-12-06 13:19:13    ~0.86     R     300*36     > 22.6

Our non-detection is consistent with Odeh et al. 2023, GCN 35270;
Strausbaugh et al. 2023, GCN 35278; Jiang et al. 2023, GCN 35280; Jiang et
al. 2023, GCN 35281; Gendre et al. 2023, GCN 35282; Sasada et al. 2023, GCN
35284; Adami et al. 2023, GCN 35286; Komesh et al. 2023, GCN 35287; Brivio
et al. 2023, GCN 35289; Malenakova et al. 2023, GCN 35292; and Pankov et
al. 2023, GCN 35299

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.

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