{
  "bibcode": "2017GCN.21395....1F",
  "body": "W. Fong (University of Arizona), T. Laskar (NRAO/UC Berkeley), K. D.\nAlexander (Harvard) and E. Berger (Harvard) report:\n\n\"We observed the position of GRB 170728B (Cenko et al., GCN 21371; Yassine\net al., GCN 21380; Stanbro & Meegan, GCN 21383) with the Karl G. Jansky\nVery Large Array (VLA) beginning on 2017 Jul 29.075 UT (2.75 hr post-burst)\nat a mean frequency of 6 GHz. We obtained a second set of observations\nbeginning on 2017 Jul 29.811 UT (20.4 hr post-burst) at mean frequencies of\n6 and 10 GHz.\n\nWe do not detect any radio counterpart in our first set of observations at\n2.75 hr, while we clearly detect a radio source in our second set of\nobservations at both frequencies at 20.4 hr at the position:\n\nRA(J2000) = 15:51:55.45\nDec(J2000) = +70:07:21.2\n\nwith an uncertainty of 0.2\" in each coordinate. This position is coincident\nwith the reported optical source (D'Avanzo et al., GCN 21372, GCN 21373;\nHeintz et al., GCN 21374; Guidorzi et al., GCN 21375; Watson et al., GCN\n21389). Given the rapid variability and positional coincidence with the\nX-ray (Osborne et al., GCN 21377) and optical afterglows, we consider this\nto be the radio afterglow of GRB 170728B.\n\nFurther observations are planned. We thank the VLA staff for quickly\nexecuting these observations.\"",
  "circularId": 21395,
  "createdOn": 1501475236000,
  "email": "wfong@email.arizona.edu",
  "subject": "GRB 170728B: VLA radio afterglow detection",
  "submitter": "Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>",
  "eventId": "GRB 170728B"
}