TITLE: GCN CIRCULAR NUMBER: 35302 SUBJECT: GRB 231205B: 1.3m DFOT Optical upper limit DATE: 23/12/07 13:20:11 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894@gmail.com> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/35302. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...