TITLE:   GCN CIRCULAR
NUMBER:  29139
SUBJECT: GRB 201221D: Swift-BAT refined analysis
DATE:    20/12/22 17:44:15 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), K. L. Page (U Leicester),
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-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 201221D (trigger #1014037)
(Page et al., GCN Circ. 29112).  The BAT ground-calculated position is
RA, Dec = 171.055, 42.152 deg which is
   RA(J2000)  =  11h 24m 13.2s
   Dec(J2000) = +42d 09' 08.4"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 23%.

The mask-weighted light curve shows a single-peaked structure that
starts at ~T-0.06 s, peaks at ~T+0.02 s, and ends at ~T+0.2 s.
T90 (15-350 keV) is 0.16 +- 0.04 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.06 to T+0.17 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.56 +- 0.13.  The fluence in the 15-150 keV band is
3.9 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T-0.44 sec in the 15-150 keV band is 5.6 +- 0.5 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/1014037/BA/