TITLE:   GCN CIRCULAR
NUMBER:  27246
SUBJECT: GRB 200227A: Swift-BAT refined analysis
DATE:    20/02/28 05:04:40 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 200227A (trigger #958592)
(Laha, et al., GCN Circ. 27234).  The BAT ground-calculated position is
RA, Dec = 56.433, 9.489 deg, which is 
   RA(J2000)  =  03h 45m 43.9s 
   Dec(J2000) = +09d 29' 22.0" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.
 
The mask-weighted light curve a couple overlapping peaks starting
at T-10 sec, peaking at T+8 sec, and ending at T+90 sec.
T90 (15-350 keV) is 32.8 +- 9.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.50 to T+87.64 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.15 +- 0.19, 
and Epeak of 156.4 +- 88.9 keV (chi squared 55.3 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 7.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+8.54 sec in the 15-150 keV band is
5.7 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.46 +- 0.05 (chi squared 63.6 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/958592/BA/