{
  "bibcode": "1998GCN...141....1F",
  "body": "D. A. Frail, (NRAO), S. R. Kulkarni (CIT), J. S. Bloom (CIT), S. G.\nDjorgovski and the BeppoSAX GRB Team report:\n\nThe radio source identified as a possible afterglow in GCN #128 has\nbrightened considerably and is exhibiting short-timescale\nvariability. During a 3.5 hour VLA run on 1998 July 7 the flux density\nat 4.86 GHz varied from 1.1 mJy to 0.75 mJy. Variations are also\npresent at 8.46 GHz but they are smaller than those at 4.86 GHz.\nSimilar fluctuations have been seen at early times toward previous\nradio afterglows and were attributed to interstellar scintillation.\n\nStart Date     1.43GHz flux   4.86GHz flux   8.46GHz flux\n\t\t(microJy)\t(microJy)    (microJy)\n---------------------------------------------------------\nJul. 4.4 UT        --\t\t  137 \t\t --\nJul. 7.3 UT\t   --\t\t  910\t\t 890 \nJul. 8.5 UT\t  120 \t\t  635 \t\t 965\n---------------------------------------------------------\n\nOn 1998 July 8 the spectrum rises with higher frequencies. Such\nbehavior is uncommon in most extragalactic radio sources but it has\nbeen seen in the early spectra of previous radio afterglows and\nattributed to synchrotron self absorption.\n\nThe radio source appears unpolarized, with a 3-sigma limit on linear\npolarization at 4.8 GHz and 8.46 GHz of ~8%. An improved position is\nR.A.=23h59m6.666s, Dec.=+08d35'7.07\" (equinox J2000). The position\nerror is approximately +/-0.05\".\n\nThe strong [OII] line emission seen toward GRB980703 (GCN#139) raises\nthe possibility of detecting the host galaxy from radio radiation\nproduced by ongoing star formation (Condon An.Rev.A&A, 30, 575,\n1992). For the assumed distance and star formation rate given in\nGCN#139 we estimate that the host galaxy will be 105, 40 and 25\nmicroJy at 1.43, 4.86 and 8.46 GHz, respectively. Thus the measurement\nat 1.43 GHz could contain a significant contribution from the host\ngalaxy.\n\nWe note that a redshift of z=0.966 (GCN #137) along with the average\nfluxes reported by Galama et al. (GCN #127) implies a lower limit to\nthe X-ray afterglow isotropic energy release of 9.5e49 ergs over the\ncourse of the 10.6 hour BeppoSAX NFI pointing.  Consistent with this\n(though it is difficult to translate BATSE count rates to flux and\nfluence) the total fluence of the GRB is likely ~0.5 -- 1 x 10^-5\nerg/cm^2 implying a total isotropic energy release of ~2 -- 5 x 10^52\nerg; this falls between the implied energies of GRB 970508 (Metzger et\nal. Nature 387, 878) and GRB 981214 (Kulkarni et al. Nature, 293, 35).\n\nThis report may be cited.",
  "circularId": 141,
  "createdOn": 899950220000,
  "email": "dfrail@nrao.edu",
  "subject": "GRB980703: Radio transient",
  "submitter": "Dale A. Frail at NRAO  <dfrail@nrao.edu>",
  "eventId": "GRB 980703"
}