TITLE: GCN CIRCULAR NUMBER: 38875 SUBJECT: GRB 250108B: 1.3m DFOT upper limit DATE: 25/01/09 16:23:09 GMT FROM: Amit Kumar Ror at ARIES mitturor77894@gmail.com
Amit K. Ror, Anshika Gupta, RKS Yadav, Shashi B. Pandey, Kuntal Mishra (ARIES) report:
We observed the field of GRB 250108B detected by Swift (Swift Observatory Team, Klingler et al. 2025, GCN 38847) 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 2025-01-08 at 21:58:57 UT, i.e., ~ 0.48 days after the Swift-BAT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We could not detect the optical emission reported by Rastinejad et al. (2025, GCN 38855) in our stacked image within the error box enhanced Swift-XRT position (Osborne et al. 2025, GCN 38848). We obtain the following 3-sigma upper limit in the stacked image:
Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ========================================================= 2025-01-08 21:58:57 ~ 0.48 R 300s*12 >21.8
The non-detection of the burst is consistent with the upper limits reported by Breeveld et al. 2025, GCN 38850 and Lipunov et al. 2025, GCN 38858.
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 catalogue. This circular may be cited.
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