TITLE: GCN CIRCULAR NUMBER: 11218 SUBJECT: GRB 100905A: Swift-BAT refined analysis DATE: 10/09/05 21:39:43 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100905A (trigger #433442) (Marshall, et al., GCN Circ. 11214). The BAT ground-calculated position is RA, Dec = 31.542, 14.919 deg, which is RA(J2000) = 02h 06m 10.0s Dec(J2000) = +14d 55' 08.2" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single peak starting at ~T-1.7 sec, peaking at ~T+0.5 sec, and ending at ~T+3 sec. T90 (15-350 keV) is 3.4 +- 0.5 sec (estimated error including systematics). The time-averaged spectrum from T-1.6 to T+2.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.09 +- 0.19. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.03 sec in the 15-150 keV band is 0.6 +- 0.1 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/433442/BA/