TITLE: GCN CIRCULAR NUMBER: 7148 SUBJECT: Swift-BAT refined analysis of short GRB 071227 DATE: 07/12/28 00:44:50 GMT FROM: Takanori Sakamoto at NASA/GSFC G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-120 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 071227 (trigger #299787) (Sakamoto, et al., GCN Circ. 7147). The BAT ground-calculated position is RA, Dec = 58.132, -55.959 deg which is RA(J2000) = 3h 52m 31.8s Dec(J2000) = -55d 57' 32" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%. The mask weighted light curve shows multiple peaks during ~2 sec duration of the burst. T90 (15-350 keV) is 1.8 +- 0.4 sec (estimated error including systematics). Therefore, this burst might be classified as a short burst. Additional BAT analysis (e.g. spectral lag) is on-going, and will be presented later. The time-averaged spectrum from T-0.1 to T+1.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.99 +- 0.22. The fluence in the 15-150 keV band is 2.2 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.09 sec in the 15-150 keV band is 1.6 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.