TITLE: GCN CIRCULAR NUMBER: 10152 SUBJECT: GRB 091109B: Swift-BAT refined analysis DATE: 09/11/10 03:19:30 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (GSFC/UMD), 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), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (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 091109B (trigger #375409) (Oates, et al., GCN Circ. 10148). The BAT ground-calculated position is RA, Dec = 112.750, -54.092 deg which is RA(J2000) = 07h 30m 59.9s Dec(J2000) = -54d 05' 30.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 76%. The mask-weighted light curve shows a single symmetrical peak of duration 0.32 seconds. There is no sign of extended emission. T90 (15-350 keV) is 0.3 +- 0.03 sec (estimated error including systematics). The time-averaged spectrum from T-0.0 to T+0.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.71 +- 0.13. The fluence in the 15-150 keV band is 1.9 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.33 sec in the 15-150 keV band is 5.4 +- 0.4 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/375409/BA/ [GCN OPS NOTE(09nov09): Per author's request, the "B" was added to the GRB name and the reference was filled in.]