TITLE:   GCN CIRCULAR
NUMBER:  27117
SUBJECT: GRB 200216B: Swift-BAT refined analysis
DATE:    20/02/17 21:26:59 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),  P. D'Avanzo (INAF-OAB),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
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+908 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 200216B (trigger #956824)
(D'Avanzo, et al., GCN Circ. 27102).  The BAT ground-calculated position is
RA, Dec = 160.452, 19.468 deg which is 
   RA(J2000)  =  10h 41m 48.4s 
   Dec(J2000) = +19d 28' 05.5" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 84%.
 
The mask-weighted light curve shows a single bright pulse followed by some
extended emission.  The main pulse has a FRED shape, starting at T-2 sec, peaking
around T+2 sec and decaying by T+18 sec.   Lower-level extended emission with
some weak pulses lasts until around T+100 sec.   T90 (15-350 keV) is 81.3 +- 13.0 sec
(estimated error including systematics).
 
The time-averaged spectrum from -0.72 to +100.33 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.81 +- 0.52, 
and Epeak of 47.6 +- 6.6 keV (chi squared 48.83 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.6 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+2.80 sec in the 15-150 keV band is
1.5 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.90 +- 0.10 (chi squared 65.47 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/956824/BA/