TITLE:   GCN CIRCULAR
NUMBER:  31297
SUBJECT: GRB 211223C: Swift-BAT refined analysis
DATE:    21/12/24 14:01:07 GMT
FROM:    Tyler Parsotan at UMBC/GSFC/CRESST II  <parsotat@umbc.edu>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien
(U Tampa), 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 211223C (trigger #1090656)
(Evans, et al., GCN Circ. 31288).  The BAT ground-calculated position is
RA, Dec = 227.165, -26.878 deg which is

   RA(J2000)  =  15h 08m 39.7s

   Dec(J2000) = -26d 52' 41.0"

with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 32%.



The BAT light curve showed a complex structure with a duration of about 20
sec. T90 (15-350 keV) is 15.00 +- 5.00 sec (estimated error including
systematics).



The time-averaged spectrum from T-13.01 to T+8.99 sec is best fit by a
simple power-law model.  The power law index of the time-averaged spectrum
is 1.15 +- 0.09.  The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-06
erg/cm2. The 1-sec peak photon flux measured from T-0.01 sec in the 15-150
keV band is 3.1 +- 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/1090656/BA/