TITLE: GCN CIRCULAR NUMBER: 42813 SUBJECT: GRB 251122A/EP251122A: 1.3m DFOT optical detection DATE: 25/11/23 20:02:06 GMT FROM: ANSHIKA GUPTA at ARIES anshika05180@gmail.com
Anshika Gupta, Debalina Kar, Pankaj Pawar, Divyanshu Janghel, Dhruv Jain, and Kuntal Misra (ARIES) report:
We observed the field of GRB251122A/ EP251122A detected by Einstein Probe (Wang et al. 2025, GCN 42799) and SVOM (Lin et al. 2025, GCN 42800) 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 2025-11-22 at 16:03:25 UT, i.e., ~ 2.15 hours after the EP trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect a faint optical afterglow in our stacked image within the error box of EP/FXT (Wang et al. 2025, GCN 42799, 42809) and SVOM/ECLAIRs (Lin et al. 2025, GCN 42800). We obtain the following preliminary magnitude in the stacked image:
Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude =============================================================== 2025-11-22 16:03:25 ~2.15 R 300s*19 22.37 +/-0.04
The optical detection of the burst is consistent with WU et al. 2025 (GCN 42801); Lipunov et al. 2025 (GCN 42802); Cheng et al. 2025 (GCN 42803); Saccardi et al. 2025 (GCN 42804); Cotter et al. 2025 (GCN 42805); Li et al. 2025 (GCN 42806); Sun et al. 2025 (GCN 42807); Ma et al. 2025 (GCN 42811) .
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.
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