TITLE: GCN CIRCULAR NUMBER: 17491 SUBJECT: GRB 150222A: Swift-BAT refined analysis DATE: 15/02/23 01:16:22 GMT FROM: Hans Krimm at NASA-GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), M. G. Bernardini (INAF-OAB), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), 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-60 to T+117 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150222A (trigger #632180) (Bernardini, et al., GCN Circ. 17486). The BAT ground-calculated position is RA, Dec = 198.787, -12.151 deg which is RA(J2000) = 13h 15m 09.0s Dec(J2000) = -12d 09' 02.0" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%. The mask-weighted light curve shows a double-peaked structure, with a first peak from T+0 to T+3 sec and a second, larger peak from T+3 to T+18 sec, followed by lower level emission out to ~T+40 sec. T90 (15-350 keV) is 15.90 +- 7.32 sec (estimated error including systematics). The time-averaged spectrum from T-0.14 to T+28.11 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.61 +- 0.08. The fluence in the 15-150 keV band is 2.2 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+5.62 sec in the 15-150 keV band is 4.7 +- 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/632180/BA/