{
  "bibcode": "2025GCN.38875....1R",
  "createdOn": 1736439789614,
  "submittedHow": "email",
  "eventId": "GRB 250108B",
  "body": "Amit K. Ror, Anshika Gupta, RKS Yadav, Shashi B. Pandey, Kuntal Mishra\n(ARIES) report:\n\nWe observed the field of GRB 250108B detected by Swift (Swift Observatory\nTeam, Klingler et al. 2025, GCN 38847) with the 1.3m Devasthal Fast Optical\nTelescope (DFOT), located at the Devasthal Observatory of the Aryabhatta\nResearch Institute of Observational Sciences (ARIES), India. The\nobservations were started on 2025-01-08 at 21:58:57 UT, i.e., ~ 0.48 days\nafter the Swift-BAT trigger. We have taken multiple frames with an exposure\ntime of 300s in the R filter. We stacked the images after the alignment. We\ncould not detect the optical emission reported by Rastinejad et al. (2025,\nGCN 38855) in our stacked image within the error box enhanced Swift-XRT\nposition (Osborne et al. 2025, GCN 38848). We obtain the following 3-sigma\nupper limit in the stacked image:\n\nDate Start_UT T_start-T0 (days) Filter  Exp time (s)  Magnitude\n=========================================================\n2025-01-08 21:58:57    ~ 0.48     R     300s*12     >21.8\n\nThe non-detection of the burst is consistent with the upper limits reported\nby Breeveld et al. 2025, GCN 38850 and Lipunov et al. 2025, GCN 38858.\n\nThe magnitude is not corrected for the Galactic extinction in the direction\nof the burst. Photometric calibration is performed using the standard stars\nfrom the USNO-B1.0 catalogue. This circular may be cited.\n",
  "subject": "GRB 250108B: 1.3m DFOT upper limit",
  "submitter": "Amit Kumar Ror at ARIES <mitturor77894@gmail.com>",
  "circularId": 38875
}