TITLE: GCN CIRCULAR NUMBER: 43067 SUBJECT: GRB 251205A: 1.3m DFOT optical upper limit DATE: 25/12/10 20:44:22 GMT FROM: ANSHIKA GUPTA at ARIES anshika05180@gmail.com
Anshika Gupta, Debalina Kar, Koshvendra Singh, Dhruv Jain, Pankaj Pawar, and Kuntal Misra (ARIES) report:
We observed the field of GRB 251205A detected by Swift (Lanava et al. 2025, GCN 43005) 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 2025-12-09 at 23:15:22.00 UT, i.e., ~ 3.98 days after the Swift 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 in our stacked image within the error box of Swift/UVOT (Lanava et al. 2025, GCN 43005). We obtain the following 3-sigma upper limit in the stacked image:
Date Start_UT T_start-T0 (Days) Filter Exp time (s) Magnitude =============================================================== 2025-12-09 23:15:22.00 ~3.98 R 300s*11 >22.9
The non-detection of the burst is consistent with (Lipunov et al. 2025, GCN 43004; Lanava et al. 2025, GCN 43005; Lipunov et al. 2025, GCN 43006; de Ugarte Postigo et al. 2025, GCN 43008; Malesani et al. 2025, GCN 43009; O’Neill et al. 2025, GCN 43010; Mandarakas et al. 2025, GCN 43011; Pankov et al. 2025, GCN 43012; Bochenek et al. 2025, GCN 43015; Klinger et al. 2025, GCN 43016; Patil et al. 2025, GCN 43019; Pérez-Fournon et al. 2025, GCN 43020; Bochenek et al. 2025, GCN 43024; Busmann et al. 2025, GCN 43026; Hagio et al. 2025, GCN 43029; Bochenek et al. 2025, GCN 43038; Mo et al. 2025, GCN 43044).
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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