TITLE: GCN CIRCULAR NUMBER: 19043 SUBJECT: GRB 160220B: Swift-BAT refined analysis DATE: 16/02/21 14:37:58 GMT FROM: Hans Krimm at NASA-GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160220B (trigger #674734) (Cummings, et al., GCN Circ. 19029). The BAT ground-calculated position is RA, Dec = 259.851, -18.123 deg which is RA(J2000) = 17h 19m 24.2s Dec(J2000) = -18d 07' 21.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 38%. The mask-weighted light curve shows a double-peaked structure from T-10 to T+40 seconds. The spacecraft slewed away from the burst location at ~T+145 sec due to a pre-planned maneuver. T90 (15-350 keV) is 31.4 +- 2.6 sec (estimated error including systematics). The time-averaged spectrum from T-7.58 to T+37.54 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.75 +- 0.20, and Epeak of 168.7 +- 56.3 keV (chi squared 39.67 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 7.0 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+6.46 sec in the 15-150 keV band is 6.6 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.20 +- 0.05 (chi squared 56.26 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/674734/BA/