TITLE: GCN CIRCULAR NUMBER: 19181 SUBJECT: GRB 160313A, Swift-BAT refined analysis DATE: 16/03/13 21:59:08 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), A. D'Ai (INAF-IASFPA), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-691 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160313A (trigger #678929) (A. D'Ai et al., GCN Circ. 19171). The BAT ground-calculated position is RA, Dec = 183.821, 57.278 deg which is RA(J2000) = 12h 15m 17.0s Dec(J2000) = +57d 16' 40.1" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted light curve shows a complex structure with several overlapping pulses. The structure starts at ~ T-5 s and ends at ~ T+45 s. T90 (15-350 keV) is 42.6 +- 6.4 sec (estimated error including systematics). The time-averaged spectrum from T-5.6 to T+44.7 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.36 +- 0.23. The fluence in the 15-150 keV band is 5.8 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+24.79 sec in the 15-150 keV band is 0.4 +- 0.1 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/678929/BA/