TITLE: GCN CIRCULAR NUMBER: 20136 SUBJECT: GRB 161105A: Swift-BAT refined analysis DATE: 16/11/05 17:50:26 GMT FROM: Amy Lien at GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), K. L. Page (U Leicester), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (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 BAT GRB 161105A (trigger #720697) (Page et al. GCN Circ. 20131). The BAT ground-calculated position is RA, Dec = 120.198, -44.763 deg which is RA(J2000) = 08h 00m 47.5s Dec(J2000) = -44d 45' 47.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T-90 s and ends at ~T+160 s. There are roughly two main pulses in the structure. The first one contains two obvious peaks at ~T0 and ~T+10s, and the second one peaks at ~T+50 s. T90 (15-350 keV) is 177.3 +- 25.8 sec (estimated error including systematics). The time-averaged spectrum from T-88.00 to T+164.81 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.02 +- 0.24, and Epeak of 159.1 +- 135.3 keV (chi squared 55.64 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 6.1 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.63 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.35 +- 0.06 (chi squared 61.67 for 57 d.o.f.). 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/720697/BA/