TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4400
SUBJECT: GRB 051227:  Refined analysis of the Swift-BAT burst
DATE:    05/12/27 22:16:06 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott@lheamail.gsfc.nasa.gov>

D. Hullinger (GSFC/UMD), L. Barbier (GSFC), S. Barthelmy (GSFC),
P. Boyd (GSFC-UMBC), J. Cummings (GSFC/NRC), E. Fenimore (LANL),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), 
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC), W. Voges (MPE)
on behalf of the Swift-BAT team:

Using the full data set from the recent telemetry downlink, we report
further analysis of Swift-BAT GRB 051227 (trigger #174738)
(Barbier, et al., GCN 4397).  The ground-analysis position is
RA,Dec 125.230,+31.953 {08h 20m 55.2s,+31d 57' 12"} (J2000)
with an uncertainty of 1.8 arcmin (radius, 90%, stat+sys).
T90 is 8.0 +- 0.2 sec.  The partial coding fraction is 97%.
The lightcurve has an initial multi-peak structure at T+0.00 sec
(FWHM of ~3.5 sec) and there is a smaller broad softer peak spanning
T+30 to T+50 sec.  Fitting a simple power law over the full interval
from T-1 to T+8 sec, the photon index is 1.31 +/- 0.22 with a fluence
of 2.3 +/- 0.3 X 10^-7 erg/cm^2.  The peak flux in a 1-sec wide window
starting at T-0.008 sec is 0.97 +/- 0.13 ph/cm^2/sec.  All values are
in the 15-150 keV band at the 90% confidence level.