{
  "submitter": "Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>",
  "circularId": 44045,
  "eventId": "GRB 260310A",
  "body": "S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),\nG. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),\nN. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB),\nL. Nava (INAF-OAB)\n\nAt 10:22:44 UT on 2026 March 14 (T_mid = 4.26 days\npost-burst) the Karl G. Jansky VLA observed the field of\nGRB 260310A / AT 2026fgk (Fermi GBM team, GCN 43951,\n43975; AstroSat CZTI collaboration, GCN 43958) in three\nbands, with central frequencies of 6, 10 and 15 GHz.\n\nThe standard 3C286 was used as bandpass and flux density\ncalibrator, while J1435+7605 served as phase calibrator.\n\nFrom a preliminary analysis, an unresolved radio source\n(Rhodes et al., GCN 44005) is clearly detected at all\nfrequencies at a position:\n\nRA: 14:37:16.1424 +- 0.001\nDec: +71:50:30.328 +- 0.01\n\nconsistent with the X-ray (Jayaraman et al., GCN 43994) and\noptical (Hinds et al., AstroNote 2026-65, GCN 43977;\nKonno et al., GCN 43977; Lipunov et al., GCN 43978;\nMartin-Carrillo et al., GCN 43979, 44000; Moreno Méndez\net al, GCN 43980; Becerra et al., GCN 43991; Watson et al.,\nGCN 44001; Lai et al., GCN 44002; Izzo et al., GCN 44003;\nMoskvitin et al., GCN 44006; Romanov, GCN 44020; Brosio et\nal., GCN 44021; Pawar et al., GCN 44022) and infrared\n(Li et al., GCN 43993; Stein et al., GCN 43996; Brivio et\nal., GCN 44004) position of the transient.\n\nThe preliminary analysis yields the following results:\n\n================================================================\nT_mid\tFreq\tPeak\tr.m.s.\tBeam\t\tPA\n[days]\t[GHz]\t[uJy/b]\t[uJy/b]\t[arcsec^2]\t[deg]\n================================================================\n4.26\t6\t3894\t8\t0.39x0.29\t-31\n4.26\t10\t6368\t13\t0.24x0.19\t3.9\n4.26\t15\t9104\t29\t0.16x0.11\t-11\n================================================================\n\nWe would like to thank the staff of the VLA for approving, executing,\nand processing the observations.\n\nThe National Radio Astronomy Observatory is a facility of the National\nScience Foundation operated under cooperative agreement by Associated\nUniversities, Inc.\n\nThese observations were carried out as part of project SF181027,\napproved in the framework of the Fermi - NRAO joint program agreement.",
  "createdOn": 1773825241766,
  "subject": "GRB 260310A / AT 2026fgk: radio detection with the VLA",
  "bibcode": "2026GCN.44045....1G",
  "submittedHow": "email"
}