{
  "submittedHow": "web",
  "subject": "GRB 260310A / AT2026fgk: TNG NIR detection",
  "eventId": "GRB 260310A",
  "body": "R. Brivio (INAF-OAB), D. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF-OACn and DARK/NBI), P. D’Avanzo (INAF-OAB), V. D’Elia (ASI-SSDC), A. Melandri (INAF-OAR), A. Rossi (INAF-OAS), M. de Pasquale (Univ. Messina), Aldo Fiorenzano (INAF-TNG), Carmen Padilla (INAF-TNG) report on behalf of the CIBO collaboration:\n\nWe observed the likely counterpart of GRB 260310A, detected by Fermi/GBM (Fermi GBM team, GCN 43951; Hamburg & Meagan, GCNC 43975) and AstroSat CZTI (Salunke et al., GCN 43958) with the Italian 3.6m TNG telescope equipped with the near-infrared camera NICS. A series of images was obtained with the J and H filters starting on 2026 March 14 at 05:11:46 UT (i.e. 96.2 hours after the burst), and lasted 40 minutes for each filter.\n\nThe optical/NIR counterpart, also reported as AT2026fgk (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moreno Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al, GCN 43996; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; L. Izzo, GCN 44003) is detected in the co-added images with the following magnitudes:\n\nJ = 17.0 +/- 0.1 (Vega, calibrated against the 2MASS catalogue),\n at a mid-time of 96.5 hr after the trigger;\n\nH = 15.9 +/- 0.1 (Vega, calibrated against the 2MASS catalogue),\n at a mid-time of 97.1 hr after the trigger.",
  "circularId": 44004,
  "createdOn": 1773499690439,
  "format": "text/plain",
  "submitter": "Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>",
  "bibcode": "2026GCN.44004....1B"
}