TITLE: GCN CIRCULAR NUMBER: 26608 SUBJECT: GRB 191227A: Swift-BAT refined analysis DATE: 19/12/28 17:57:54 GMT FROM: Amy Lien at GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU), 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 191227A (trigger #946344) (Melandri et al., GCN Circ. 26595). The BAT ground-calculated position is RA, Dec = 319.172, -16.717 deg which is RA(J2000) = 21h 16m 41.4s Dec(J2000) = -16d 43' 02.5" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 13%. The mask-weighted light curve shows many overlapping pulses that starts from ~T-30 s and ends at ~T+105 s. Several obvious peaks can be seen at ~T0, ~T+3 s, ~T+5 s, and ~T+11 s, respectively. T90 (15-350 keV) is 58.5 +- 14.4 sec (estimated error including systematics). The time-averaged spectrum from T-30.55 to T+105.93 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.30 +- 0.05. The fluence in the 15-150 keV band is 2.5 +- 0.1 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from T+5.28 sec in the 15-150 keV band is 21.8 +- 1.3 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/946344/BA/