{
  "bibcode": "2005GCN..4388....1N",
  "body": "J. Norris (GSFC), T. Sakamoto (GSFC/NRC), D. Band (GSFC/UMBC), S. Barthelmy (GSFC)\non behalf of the Swift-BAT team:\n\nThe time profile of GRB 051221A binned to 1 ms resolution reveals\nthat the initial pulse structure (GCN 4363 & 4365) comprises 3 separate pulses\nof FWHM ~10-15 ms with peak intensities of ~175,000 counts per sec.\nWe note for comparison that GRB 050525A, the brightest long burst\nso far detected by BAT (in one year) had a peak count rate\nof 101,000 cts/sec (corrected to match the same partial-coding as 051221A\nof 63%).  The GRB 051221A time profile is available at:\nhttp://swift.gsfc.nasa.gov/docs/swift/results/releases/images/GRB051221A/\n\nNo extended emission is evident in this burst in the interval 30-120 sec\nafter the initial pulse structure.  The 3 sigma upper limit is 1.16 counts/cm2.\nThe ratio of (extended emission, 15-50 keV) / (initial pulse complex 15-150 keV)\nis < 0.1 (3 sigma).  The same ratio for GRB 050724 is 1.9.\n\nThe spectral lag is negligible, 0.0+-0.4 ms (0.8+-0.5 ms), between the\n15-25 and 50-100 keV (25-50 and 100-350 keV) energy bands -- typical\nof spectral lags in short bursts (Norris & Bonnell, submitted to ApJ).\n\nWe estimate roughly that the peak flux of GRB 051221A lies in the upper 3%\nof short bursts detectable by the BAT.",
  "circularId": 4388,
  "createdOn": 1135270949000,
  "email": "Scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 051221A:  Refined spectral and temporal analysis of the Swift-BAT short hard burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <Scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 051221A"
}