TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4003 SUBJECT: GRB 050916: Swift-BAT refined analysis DATE: 05/09/19 16:16:05 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift E. Fenimore (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), J. Nousek (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Tripicco (GSFC-SSAI), J. Tueller (GSFC), on behalf of the Swift-BAT team: Using the complete data set from T-300 to T+300 sec, we report further analysis of Swift-BAT GRB 050916 (trigger #155408) (Morris, et al., GCN 3991). The refined BAT ground position is (RA,Dec) = 136.005, -51.411 {09h 04m 01.1s,-51d 24' 39"} [deg; J2000] +- 1.8 arcmin, (radius, sys+stat, 90% containment). This is 1.4 arcmin from the XRT refined position reported by Morris et al. (GCN 3996), The partial coding was 41%. The light curve shows a broad peak from T+0 to T+66 and a second weaker peak from T+80 to T+100. T90 (15-150 keV) is (90 +- 10) sec (estimated error including systematics). The power law index of the time-averaged spectrum is 1.83 +- 0.32. The fluence in the 15-150 keV band is (1.1 +- 0.4) x 10^-6 erg/cm^2. The 1-sec peak photon flux measured from T+44 sec in the 15-150 keV band is (0.66 +- 0.23) ph/cm2/sec. All the quoted errors are at the 90% confidence level.