TITLE: GCN CIRCULAR NUMBER: 44022 SUBJECT: GRB 260310A / AT2026fgk: 1.3m DFOT optical observations DATE: 26/03/15 17:21:19 GMT FROM: pawarpankaj1492@gmail.com Pankaj Pawar, Debalina Kar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the likely optical counterpart of GRB 260310A, 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 2026-03-14 at 18:29:38 UT, approximately 109.54 hours (~4.56 days) after the trigger. The reported optical couterpart AT2026fgk (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, Moren Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984, Pursiainen et al., Becerra et al., GCN 43991; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; L. Izzo, GCN 44003; Brivio et al., GCN 44004; Rhodes et al., GCN 44005; Moskvitin et al., GCN 44006; Brosio et al., GCN 44021) is clearly detected in a single 100s R-band frame. We derive the following magnitude from the stacked image: Date Start_UT T_start-T0(days) Filter Exp time (s) Magnitude =============================================================== 2026-03-14 18:29:38 ~4.56 R 100s*1 18.54 ± 0.12 The reported magnitude is calibrated using Pan-STARRS field stars and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44022. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...