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GCN Circular 20967

Subject
GRB 170331A: Swift-BAT refined analysis
Date
2017-04-01T06:15:10Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), N. Gehrels (GSFC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB), 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+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170331A (trigger #744791)
(Melandri et al., GCN Circ. 20946).  The BAT ground-calculated position is
RA, Dec = 323.778, -24.406 deg which is
  RA(J2000)  =  21h 35m 06.8s
  Dec(J2000) = -24d 24' 22.4"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 18%.

The mask-weighted light curve shows a weak pulse that starts at ~T-3 s,
peaks at ~T+1 s, and ends at ~T+17 s. T90 (15-350 keV) is 17.57 +- 2.57 sec
(estimated error including systematics).

The time-averaged spectrum from T-2.78 to T+17.17 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.37 +- 1.19,
and Epeak of 48.2 +- 12.7 keV (chi squared 61.51 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 9.7 +- 1.6 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+0.42 sec in the 15-150 keV band is
1.2 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.86 +- 0.21 (chi squared 68.07 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/744791/BA/
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