TITLE: GCN CIRCULAR NUMBER: 10141 SUBJECT: GRB 091109: Swift-BAT refined analysis DATE: 09/11/09 11:34:40 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091109 (trigger #375246) (Oates, et al., GCN Circ. 10138). The BAT ground-calculated position is RA, Dec = 309.252, -44.177 deg, which is RA(J2000) = 20h 37m 00.5s Dec(J2000) = -44d 10' 36.0" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 19%. The mask-weighted light curve shows a couple overlapping peaks. The first starts at ~T-15 sec, peaks at ~T+10 sec. The second (weaker) peaks at ~T+40 sec and ends at ~T+60 sec. T90 (15-350 keV) is 48 +- 17 sec (estimated error including systematics). The time-averaged spectrum from T-0.8 to T+51.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.31 +- 0.25. The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+8.20 sec in the 15-150 keV band is 1.3 +- 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/375246/BA/