TITLE:   GCN CIRCULAR
NUMBER:  20325
SUBJECT: GRB 161220A: Swift-BAT refined analysis
DATE:    16/12/21 18:35:58 GMT
FROM:    Tilan Ukwatta at LANL  <tilan.ukwatta@gmail.com>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), V. D'Elia (ASDC),
N. Gehrels (GSFC), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-61 to T+243 sec from the
recent telemetry downlink, we report further analysis
of BAT GRB 161220A (trigger #727610) (D'Elia, et al.,
GCN Circ. 20302).  The BAT ground-calculated position
is RA, Dec = 350.841, -47.480 deg which is
   RA(J2000)  =  23h 23m 21.7s
   Dec(J2000) = -47d 28' 47.3"
with an uncertainty of 2.0 arcmin, (radius, sys+stat,
90% containment). The partial coding was 100%.

The mask-weighted light curve shows a single episode
that starts around T-4 sec, peaks around T+3 sec and
ends at ~T+4 sec. T90 (15-350 keV) is 6 +- 1 sec
(estimated error including systematics).

The time-averaged spectrum from T-2.24 to T+4.66 sec
is best fit by a simple power-law model.  The power
law index of the time-averaged spectrum is 2.01 +- 0.25.
The fluence in the 15-150 keV band is
1.7 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux
measured from T+2.42 sec in the 15-150 keV band
is 0.5 +- 0.1 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/727610/BA/