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GCN Circular 23166

GRB 180821A: Swift-BAT refined analysis
2018-08-22T13:15:43Z (6 years ago)
Hans Krimm at NSF/NASA-GSFC <>
H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC),  J. R. Cummings (CPI),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), A. Tohuvavohu (PSU), 
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 180821A (trigger #854578)
(Tohuvavohu, et al., GCN Circ. 23158).  The BAT ground-calculated position is
RA, Dec = 7.739, -38.612 deg which is 
 RA(J2000)  =  00h 30m 57.4s 
 Dec(J2000) = -38d 36' 41.9" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 17%.

The mask-weighted light curve showed a broad peak with some structure, 
running from ~T+0 to T+70 sec. T90 (15-350 keV) is 64.00 +- 22.6 sec 
(estimated error including systematics).

The time-averaged spectrum from T+1.00 to T+65.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.79 +- 0.31.  The fluence in the 15-150 keV band is 1.4 +- 0.3 x 10^-6 erg/cm2.
Since the peak was so broad, the automated analysis software was unable to 
derive a significant peak photon flux at the highest point in the light curve, T+56.5 sec.
All the quoted errors are at the 90% confidence level. 

The results of the batgrbproduct analysis are available at
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