TITLE: GCN CIRCULAR NUMBER: 18148 SUBJECT: GRB 150817A: Swift-BAT refined analysis DATE: 15/08/17 14:18:27 GMT FROM: Scott Barthelmy at NASA/GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 150817A (trigger #652334) (D'Elia, et al., GCN Circ. 18143). The BAT ground-calculated position is RA, Dec = 249.635, -12.050 deg, which is RA(J2000) = 16h 38m 32.3s Dec(J2000) = -12d 03' 01.7" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%. The mask-weighted light curve shows multiple strong peaks starting at ~T-20, with the brightest peak at ~T+12 sec and ending at ~T+70 sec. T90 (15-350 keV) is 38.8 +- 2.1 sec (estimated error including systematics). The time-averaged spectrum from T-16.76 to T+53.28 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 +- 0.04. The fluence in the 15-150 keV band is 5.9 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+11.22 sec in the 15-150 keV band is 9.6 +- 0.3 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/652334/BA/