TITLE: GCN CIRCULAR NUMBER: 10197 SUBJECT: GRB 091127: Swift-BAT refined analysis DATE: 09/11/28 03:23:46 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), E. Troja (NASA/GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091127 (trigger #377179) (Troja, et al., GCN Circ. 10191). The BAT ground-calculated position is RA, Dec = 36.581, -18.948 deg, which is RA(J2000) = 02h 26m 19.5s Dec(J2000) = -18d 56' 51.1" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 4%. The mask-weighted light curve shows three main peaks. The first starts at ~T-0.3 sec and peaks at ~T0. The second peaks at ~T+1.1 sec. The third peaks at ~T+7 sec and ends at ~T+10 sec. T90 (15-350 keV) is 7.1 +- 0.2 sec (estimated error including systematics). The time-averaged spectrum from T-0.4 to T+7.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.05 +- 0.07. The fluence in the 15-150 keV band is 9.0 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.25 sec in the 15-150 keV band is 46.5 +- 2.7 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/377179/BA/