TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4237 SUBJECT: GRB 051109B: Swift-BAT refined analysis DATE: 05/11/09 21:44:23 GMT FROM: Takanori Sakamoto at NASA/GSFC D. Hullinger (UMD), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team: Using the data set from T-300 to T+300 sec from the recent telemetry downlink, we report further analysis of BAT GRB 051109B (trigger #163170) (Tagliaferri, et al., GCN 4222). The BAT ground-calculated position is (RA,Dec) = 345.468, +38.666 {23h 1m 52.3s, 38d 39' 58"} [deg; J2000] +-2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 90%. The light curve has a single peak. There is no strong emission in the 100-350 keV band. T90 (15-350 keV) is (15 +- 1) sec (estimated error including systematics). The power law index of the time-averaged spectrum is 1.96 +- 0.25. The fluence in the 15-150 keV band is (2.7 +- 0.4) x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T0+0.24 sec in the 15-150 keV band is (0.5 +- 0.1) ph/cm2/sec. All the quoted errors are at the 90% confidence level.