{
  "bibcode": "2011GCN.12214....1B",
  "body": "G. Bower, S. B. Cenko, J. S. Bloom (UC Berkeley) and B. D. Metzger\n(Princeton) report on behalf of a larger collaboration:\n\nWe have obtained a second epoch of long-baseline interferometry with the\nVLBA of the unusual high-energy transient Sw J1644+57 (GRB 110328A; Levan\net al, Science, 333, 199, 2011; Bloom et al, Science, 333, 203, 2011;\nBurrows et al., astro-ph/1104.4787; Zauderer et al., astro-ph/1106.3568).\nObservations were obtained on 2011 July 17 at 8.4 and 22 GHz with\nrecording bandwidth of 512 Mbps. Preliminary analysis of images at both\nfrequencies reveals a compact (i.e., unresolved) source with flux\ndensities of 15 and 12 mJy, respectively. Errors in the flux density are\nset by the amplitude scale and are estimated at 10%. The 8.4 GHz\nlocalization is consistent with the position obtained from our previous\nepoch of VLBA observations on 2011 April 1 and 3 (Levan et al., Science\n333, 199, 2011; see also Zauderer et al., astro-ph/1106.3568) at the level\nof ~ 300 uas. If we assume expansion with a constant speed from the time\nof the initial high-energy detections of this source, this places an upper\nlimit on the average outflow Lorentz factor of Gamma <~ 5.",
  "circularId": 12214,
  "createdOn": 1312053766000,
  "email": "cenko@srl.caltech.edu",
  "subject": "Sw J1644+57 (GRB 110328A): Continued VLBA Observations",
  "submitter": "S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>",
  "eventId": "GRB 110328A"
}