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GCN Circular 19840

Subject
GRB 160821A: Swift-BAT refined analysis
Date
2016-08-22T14:04:04Z (8 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. H. Siegel (PSU), 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 160821A (trigger #709351)
(Siegel, et al. GCN Circ. 19830).  The BAT ground-calculated position is
RA, Dec = 171.254, 42.345 deg which is
  RA(J2000)  =  11h 25m 00.9s
  Dec(J2000) = +42d 20' 43.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.

The mask-weighted light curve shows a complex structure with many
overlapping pulses that starts at ~T-3 s and extends beyond T+117s,
when the the burst went out of the BAT FOV due to a pre-planned slew.
The burst flux was rising during the slew, so it is possible that the BAT
detector missed the peak emission. The main peak that is visible in
the BAT light curve occurs at ~T+114 s.

The time-averaged spectrum from T-2.61 to T+115.17 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.52 +- 0.06.  The fluence in the 15-150 keV band is 7.2 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+113.51 sec in the 15-150 keV band
is 2.8 +- 0.6 ph/cm2/sec.  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/709351/BA/
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