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. C. Morris (GWU/GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+350 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100728B (trigger #430172) (Morris, et al., GCN 11009). The BAT ground-calculated position is RA, Dec = 44.051, 0.296 deg which is RA(J2000) = 02h 56m 12.2s Dec(J2000) = +00d 17' 45.9" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 11%. The mask-weighted light curve shows a single peak of duration 10 seconds, starting at T-2 sec and continuing at a low level to about T+20 sec. An observing constraint moved the burst out of the BAT field of view at T+350 sec, but there is no sign of extended emission from this burst. T90 (15-350 keV) is 12.1 +- 2.4 sec (estimated error including systematics). The time-averaged spectrum from T-1.7 to T+13.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.55 +- 0.14. The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10-6 erg/cm2. The 1-sec peak photon flux measured from T+0.18 sec in the 15-150 keV band is 3.5 +- 0.5 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/430172/BA/

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