TITLE:   GCN CIRCULAR
NUMBER:  20308
SUBJECT: GRB 161219B: Swift-BAT refined analysis
DATE:    16/12/20 18:22:59 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

 Using the data set from T-240 to T+962 sec from the recent telemetry downlink, 
we report further analysis of BAT GRB 161219B (trigger #727541) 
(D'Ai, et al., GCN Circ. 20296). The BAT ground-calculated position is 
RA, Dec = 91.717, -26.801 deg which is 	
 	RA(J2000) = 06h 06m 52.0s 
 	Dec(J2000) = -26d 48' 02.1” 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). 
The partial coding was 50%. 

 The mask-weighted light curve shows a soft, weak peak at around T-10 sec,then the
main peak starts at T-2 sec, peaks at T+2 sec and decays to background by T+8 sec.
T90 (15-350 keV) is 6.94 +- 0.79 sec (estimated error including systematics).

The time-averaged spectrum from T-0.54 to T+8.38 sec is best fit by a power law 
with an exponential cutoff. This fit gives a photon index 1.29 +- 0.35, 
 and Epeak of 61.9 +- 16.8 keV (chi squared 44.89 for 56 d.o.f.). For this 
model the total fluence in the 15-150 keV band is 1.5 +- 0.1 x 10^-6 erg/cm2 
and the 1-sec peak flux measured from T+1.56 sec in the 15-150 keV band is 
5.3 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index 
of 1.84 +- 0.08 (chi squared 53.05 for 57 d.o.f.). 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/727541/BA/