TITLE: GCN CIRCULAR NUMBER: 12217 SUBJECT: GRB 110731A: Swift-BAT refined analysis DATE: 11/07/31 13:58:26 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+402 sec from the recent telemetry downlink, we report further analysis of BAT GRB 110731A (trigger #458448) (Oates, et al., GCN Circ. 12215). The BAT ground-calculated position is RA, Dec = 280.513, -28.536 deg, which is RA(J2000) = 18h 42m 03.1s Dec(J2000) = -28d 32' 10.0" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The mask-weighted light curve shows many overlapping peaks starting at ~T-1.5 sec, peaking at +T_zero, and ending at ~T+8 sec with a long exponential decay lasting out to ~T+80 sec. T90 (15-350 keV) is 38.8 +- 13.0 sec (estimated error including systematics). The time-averaged spectrum from T-1.3 to T+80.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.15 +- 0.05. The fluence in the 15-150 keV band is 6.0 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.26 sec in the 15-150 keV band is 11.0 +- 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/458448/BA/