TITLE: GCN CIRCULAR 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 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.