TITLE: GCN CIRCULAR NUMBER: 9915 SUBJECT: GRB 090916, Swift-BAT refined analysis DATE: 09/09/16 12:54:14 GMT FROM: Hans Krimm at NASA-GSFC 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. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), E. Troja (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of the short BAT GRB 090916 (trigger #362818) (Troja, et al., GCN Circ. 9913). The BAT ground-calculated position is RA, Dec = 126.582, 25.941 deg which is RA(J2000) = 08h 26m 19.6s Dec(J2000) = +25d 56' 27.3" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%. The mask-weighted light curve consisted of a single peak of 0.32 sec duration starting at T-0.128 sec, followed by low-level emission extending out to about T+70 sec. T90 (15-350 keV) is 63.4 +- 15.2 sec (estimated error including systematics). The time-averaged spectrum from T-0.0 to T+68.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.42 +- 0.33. The total fluence in the 15-150 keV band is 9.5 +- 1.8 x 10-7 erg/cm2. The peak second starting from T-0.036 sec is best fit by a simple power-law model. The power law index of the peak-second spectrum is 1.41 +- 0.28. The 1-sec peak fluence in the 15-150 keV band is 1.5 +- 0.26 x 10-7 erg/cm2. The 1-sec peak photon flux 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/362818/BA/