TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3982 SUBJECT: GRB 050915: Swift-BAT refined analysis DATE: 05/09/15 15:53:42 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift S. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hinshaw (GSFC-SPSYS), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team: Using the data set from T-100 to T+300 sec from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050915 (trigger #155242) (Grupe, et al., GCN 3977). The refined BAT ground position is RA,Dec = 81.682d,-28.010d {5h26m43.7s,-28d0'36"} [J2000] +/- 1.4 arcmin, (radius, sys+stat, 90% containment). This position is 25 arcsec from the XRT afterglow position reported in Kennea, et al. (GCN circ. 3979). The partial coding was 75%. The light curve shows about seven 2-second long peaks from T-10 to T+20 sec and one more peak at about T+43 sec. T90 (15-350 keV) is 53 +- 3 sec (estimated error including systematics). The time-averaged spectrum from T-8 to T+56 sec is well fit by a simple power law. The power law index is 1.36 +- 0.16. The fluence in the 15-150 keV band is 8.8 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+13.7 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.