TITLE: GCN CIRCULAR NUMBER: 44051 SUBJECT: GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT DATE: 26/03/19 14:57:05 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180@gmail.com> Anshika Gupta, Kumar Pranshu, Dhruv Jain, Debalina Kar, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB260310A/AT2026fgk detected by Fermi/GBM (Fermi GBM team, GCN 43951) and AstroSat(Salunke et al., GCN 43958) 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 began on 2026-03-17 at 20:33:36.00 UT, i.e., ~ 7.65 days after the Fermi/GBM trigger. We have taken multiple frames with an exposure time of 300s in the I filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================ 2026-03-17 20:33:36.00 ~7.65 I 300s*3 18.01 +/-0.02 The optical detection of the burst is consistent with Lipunov et al., GCN 43954; Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979, 44000; Moreno Méndez et al., GCN 43980; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al., GCN 43996; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003; Brivio et al., GCN 44004; Moskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et al., GCN 44021; Pawar et al., GCN 44022; Belkin et al., GCN 44043; Li et al., GCN 44044. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/44051. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...