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GCN Circular 23188

Subject
GRB 180828A: Swift-BAT refined analysis
Date
2018-08-29T16:00:35Z (6 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
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 180828A (trigger #856977)
(Beardmore et al., GCN Circ. 23182).  The BAT ground-calculated position is
RA, Dec = 268.704, -25.791 deg which is
  RA(J2000)  =  17h 54m 49.1s
  Dec(J2000) = -25d 47' 28.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 19%.

The mask-weighted light curve shows a few overlapping pulses that starts at
~ T-7 s and ends at ~T+2 s, with some weak tail emission that lasts till
~ T+30 s. T90 (15-350 keV) is 14.0 +- 8.0 sec (estimated error including systematics).

The time-averaged spectrum from T-7.29 to T+28.71 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.89 +- 0.06.  The fluence in the 15-150 keV band is 8.8 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band
is 17.8 +- 0.9 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The BAT temporal and spectral characteristics are consistent with
those of a GRB.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/856977/BA/
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