{
  "bibcode": "2006GCN..5761....1P",
  "body": "A. Parsons (GSFC), L. Barbier (GSFC), S.D. Barthelmy (GSFC),\nJ. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),\nD. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),\nD. Palmer (LANL), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),\nM. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),  D.N. Burrows (PSU),\nV. Mangano, T. Mineo, G. Cusumano, B. Sbarufatti (INAF-IASFPA),\nS.B. Pandey (UCL-MSSL)\non behalf of the Swift team:\n \nUsing the data set from T-239 to T+963 sec from recent telemetry downlinks,\nwe report further analysis of BAT possible GRB 061027 (trigger #235645)\n(Stamatikos, et al., GCN Circ. 5760).  The BAT ground-calculated position\nis RA,Dec = 270.992, -82.239 deg {18h 3m 58.1s, -82d 14' 19.9\"} (J2000)\n+- 3.7 arcmin, (radius, sys+stat, 90% containment).  The partial coding was 68%.\n \nThe event starts ~100 sec before the trigger and extends to ~T+70 sec.\nAll of the emission is in the 15-50 keV band -- there is nothing above 50 keV.\nBecause this event is very weak, we had to use 10-sec binning for the lightcurve.\nThere appears to be no statistically significant structure in the lightcurve.\nT90 (15-350 keV) is 150 +- 20 sec (estimated error including systematics).\n \nThe time-averaged spectrum from T-100 to T+70 is best fit by a simple\npower-law model.  The power law index of the time-averaged spectrum is\n1.91 +- 0.48.  The fluence in the 15-150 keV band is 4.7 +- 1.5 x 10^-7 erg/cm2.\nThe 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV\nband is 0.08 +- 0.02 ph/cm2/sec.  All the quoted errors are at the 90%\nconfidence level. \n\nGiven the very low flux, the somewhat low detection significance, and\nthe soft spectrum for this event, we can not determine if this is a\nlong soft GRB or some hard x-ray transient from an unknown source.\nThe position in galactic coordinates is l, b = 311, -25, so the source\nis off the plane but still possibly a galactic transient.  We can not rule out\nthe possibility that this event is due to a chance statistical fluctuation\nin the image and rate domains.\n\nXRT observed the field of GRB061027 for 1.5 ks in PC mode starting\nat 10:17:37 UT (152 seconds after the BAT trigger).  No source has been\ndetected within the BAT error circle down to a limiting flux\nof 3.6e-13 erg cm^-2 s^-1.  This is unusually low for a GRB afterglow\nat this point after a trigger, and suggests that this event may be\neither an unusual GRB or due to some other source, either transient or noise.\n\nUVOT began observing the field around 133 sec after the BAT trigger.\nNo afterglow candidate is found within the BAT error circle.\nThe 3-sigma upper limit of the UVOT filters are given below.\n\nFilter    T_start   T_stop   Exposure(s)   Mag (3-sig Upper limit)\nV         133       6777     805           20.41\nB         735       6163     206           20.40\nU         711       5958     216           20.04\nW1        687       5753     235           19.96\nM2        663       6839     292           19.95\nW2        763       6573     216           20.29\nWhite     152       6367     501           21.10",
  "circularId": 5761,
  "createdOn": 1161979373000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 061027, Swift refined analysis of a possible burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 061027"
}