{
  "createdOn": 1773246744994,
  "submittedHow": "email",
  "circularId": 43963,
  "submitter": "Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>",
  "subject": "GRB 260131A/B: radio detection with the VLA",
  "eventId": "GRB 260131A",
  "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 00:39:44 UT on 2026 February 5 (T_mid = 4.78 days\npost-burst) the Karl G. Jansky VLA observed the field of\nGRB 260131A/B (Fermi GBM team, GCN 43579, 43585; Sugai et\nal., GCN 43580; Konus-Wind team, GCN 43590; Insight-HXMT\nteam, GCN 43591; GRID Collaboration, GCN 43605) in three\nbands, with central frequencies of 6, 10 and 15 GHz.\n\nThe standard 3C48 was used as bandpass, flux density\nand phase calibrator.\n\nFrom a preliminary analysis, an unresolved radio source\nis detected at a position (J2000):\n\nRA: 01:38:51.308 +- 0.001\nDec: +34:19:40.84 +- 0.01\n\nconsistent with the X-ray (Sugai et al., GCN 43580;\nJiang et al., GCN 43600;), optical (GOTO collaboration,\nGCN 43586; Lee et al., GCN 43587; García García, GCN 43599;\nJayaraman et al., GCN 43606; Zhu et al., GCN 43607; KAIT\nGRB team, GCN 43609; MISTRAL GRB collaboration, GCN 43610;\nVolnova et al., GCN 43632, 43670; Gupta et al., GCN 43708)\nand infrared (Shi et al., GCN 43601) position of the\ntransient.\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================================================================\n4.78\t6\t669\t6\t0.94x0.34\t74\n4.78\t10\t1018\t6\t0.60x0.21\t70\n4.78\t15\t1671\t9\t0.49x0.15\t68\n================================================================\n\nNo source is detected with a >3sigma confidence level at the\naforementioned position in the VLASS.\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."
}