TITLE: GCN CIRCULAR NUMBER: 17330 SUBJECT: GRB 150120B: Swift-BAT refined analysis DATE: 15/01/20 22:51:16 GMT FROM: Amy Lien at GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC) N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150120B (trigger #627170) (V. D'Elia, et al., GCN Circ. 17314). The BAT ground-calculated position is RA, Dec = 39.309, 8.064 deg which is RA(J2000) = 02h 37m 14.1s Dec(J2000) = +08d 03' 50.3" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%. The mask-weighted light curve shows a multi-peaked structure starts at ~ T-20 s and ends at ~ T+10 s, with the main peak at ~ T+0 s. T90 (15-350 keV) is 24.30 +- 3.39 sec (estimated error including systematics). The time-averaged spectrum from T-17.64 to T+9.63 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.20 +- 0.25. The fluence in the 15-150 keV band is 5.4 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.58 sec in the 15-150 keV band is 1.2 +- 0.2 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/627170/BA/