{
  "bibcode": "2009GCN.10217....1K",
  "body": "H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),\nA. P. Beardmore (U Leicester), J. R. Cummings (CRESST/GSFC/UMBC),\nE. Hoversten (PSU), on behalf of the Swift team.\n\nUsing the Swift/BAT data set from T-60 to T+236 sec and the\nXRT data set beginning at T+58 minutes from recent telemetry\ndownlinks, we report that BAT trigger 356516 (reported as\npossible GRB 091130A, Krimm et al, Circ 10212) is probably\nnot a GRB.  We base this conclusion on the low significance\nin the BAT and the lack of a counterpart in the XRT.\nHowever, we can not rule out that this is an astrophysical\nevent which was extended in duration in the BAT (the\noriginal trigger was a 400-sec integration), but rapidly\nfading prior to the XRT observations.\n\nThe BAT image shows a 3.5 sigma bump and the mask-weighted\nlight curve shows an integrated 5-sigma positive excess out\nto T+236 sec.  If the source is real, it is at RA, Dec =\n161.854, +11.580 deg with an uncertainty of 4.5 arcmin,\n(radius, sys+stat, 90% containment). The partial coding is 97%.\n\nIn 2.57 ks of Swift-XRT photon counting mode data beginning\nat T+58 minutes, we do not detect any X-ray source in the\nBAT error circle to a 3 sigma upper limit count rate\nof 8.0e-3 count/s. This corresponds to a  0.3-10 keV\nobserved flux limit of 3.1e-13 erg cm-2 s-1, assuming a\ntypical counts-to-flux conversion factor\nof 3.9e-11 erg cm-2 count-1.\n\nUVOT took a finding chart exposure of 150 seconds with\nthe White filter starting 3592 seconds after the BAT trigger.\nNo credible afterglow candidate has been found in the initial\ndata products. The 2.7'x 2.7' sub-image covers 25% of the BAT\nerror circle. The typical 3-sigma upper limit has been\nabout 19.6 mag. The 8'x8' region for the list of sources\ngenerated on-board covers 100% of the BAT error circle.\nThe list of sources is typically complete to about 18 mag.\nNo correction has been made for the expected extinction\ncorresponding to E(B-V) of 0.03.",
  "circularId": 10217,
  "createdOn": 1259620690000,
  "email": "hans.krimm@nasa.gov",
  "subject": "Swift trigger 377436 (possible GRB 091130A) is not a burst",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>",
  "eventId": "GRB 091130A"
}