TITLE:   GCN CIRCULAR
NUMBER:  31326
SUBJECT: GRB 211227A: Swift-BAT refined analysis
DATE:    21/12/28 17:01:31 GMT
FROM:    Tyler Parsotan at UMBC/GSFC/CRESST II  <parsotat@umbc.edu>

A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC),  H. A. Krimm (NSF), S. Laha
(GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan
(GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT
team):



Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 211227A (trigger #1091101)
(Beardmore et al., GCN 31316).  The BAT ground-calculated position is RA,
Dec = 132.144, -2.736 deg which is

   RA(J2000)  =  08h 48m 34.5s

   Dec(J2000) = -02d 44' 10.9"

with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 41%.



The BAT light curve showed a complex structure with a duration of about 100
sec. T90 (15-350 keV) is 83.79 +- 8.47 sec (estimated error including
systematics).



The time-averaged spectrum from 0.04 to 126.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is 1.60
+- 0.05.  The fluence in the 15-150 keV band is 8.0 +- 0.2 x 10^-06
erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150
keV band is 5.1 +- 0.4 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/1091101/BA/