TITLE: GCN CIRCULAR NUMBER: 38818 SUBJECT: GRB 250101A: 1.3m DFOT optical afterglow detection DATE: 25/01/04 06:50:02 GMT FROM: ANSHIKA GUPTA at ARIES anshika05180@gmail.com
Anshika Gupta, Amit K. Ror, Mamta, Kuntal Misra, and Shashi B. Pandey (ARIES) report:
We observed the field of GRB 250101A detected by Swift-BAT (GCN 38752) 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 2025-01-01 at 17:14:04 UT, i.e., ~ 3.85 hours after the Swift-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 clearly detected optical afterglow in our stacked image within the error box of the enhanced Swift-XRT position by Goad et al. 2025 (GCN 38761). We obtained the following preliminary magnitude in the stacked image:
Date Start_UT T_start-T0 (hour) Filter Exp time (s) magnitude
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2025-01-01 17:14:04 ~3.85 hour R 300*12 19.955+-0.003
Our detection is consistent with Page et al. 2025 (GCN 38752); Li et al. 2025 (GCN 38753); Mohan et al. 2025(GCN 38754); Zhu et al. 2025 (GCN 38755); Budnev et al. 2025 (GCN 38756); SVOM/C-GFT team 2025 (GCN 38758); Zhu et al. 2025 (GCN 38759); Moskvitin et al. 2025(GCN 38762, GCN 38765); Odeh et al. 2025 (GCN 38763); Hu et al. 2025 (GCN 39764); D'Avino et al. 2025(GCN 38768); Coca et al. 2025 (GCN 38769); Leonini et al. 2025(GCN 38771); Zhang et al. 2025 (GCN 38774); Siegel et al. 2025 (GCN 38775); Komesh et al. 2025 (GCN 38777); Ghosh et al. 2025 (GCN 38779); Moskvitin et al. 2025 (GCN 38780); Komesh et al. 2025 (GCN 38790); Bochenek et al. 2025 (GCN 38798); Lapido et al. 2025 (GCN 38810).
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.
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