TITLE:   GCN CIRCULAR
NUMBER:  19106
SUBJECT: GRB 160227A, Swift-BAT refined analysis
DATE:    16/02/28 17:12:21 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+800 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160227A (trigger #676423)
(Siegel et al., GCN Circ. 19098).  The BAT ground-calculated position is
RA, Dec = 195.034, 78.672 deg which is
  RA(J2000)  =  13h 00m 08.1s
  Dec(J2000) = +78d 40' 19.9"
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~ T0-100 s and ends at ~ T0+270 s. There are roughly four pulses with peaks
at ~ T0-100 s, ~ T0-20 s, ~ T0+100 s, and ~ T0+200 s, respectively.
T90 (15-350 keV) is 316.5 +- 75.4 sec (estimated error including systematics).

The time-averaged spectrum from T-99.8 to T+236.2 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.75 +- 0.51,
and Epeak of 65.8 +- 16.4 keV (chi squared 40.42 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+198.62 sec in the 15-150 keV band is
0.6 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.65 +- 0.10 (chi squared 51.62 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/676423/BA/