TITLE: GCN CIRCULAR NUMBER: 19961 SUBJECT: GRB 160927A: Swift-BAT refined analysis DATE: 16/09/28 07:13:26 GMT FROM: Takanori Sakamoto at AGU A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), S. L. Gibson (U Leicester), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), 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-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160927A (trigger #713782) (Gibson, et al., GCN Circ. 19952). The BAT ground-calculated position is RA, Dec = 256.268, 17.334 deg which is RA(J2000) = 17h 05m 04.2s Dec(J2000) = +17d 20' 01.8" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%. The mask-weighted light curve in 16 msec binning shows at least two peaks. The first peak starts at T-0.2 sec, peaks at T+0.2 sec and ends at T+0.3 sec. The second peak starts at T+0.3 sec, peaks at T+0.4 sec and ends at T+0.5 sec. T90 (15-350 keV) is 0.48 +- 0.10 sec (estimated error including systematics). The time-averaged spectrum from T+0 to T+0.54 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.12 +- 0.26. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.23 sec in the 15-150 keV band is 1.9 +- 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/713782/BA/