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GCN Circular 23264

Subject
GRB 180924A: Swift-BAT refined analysis
Date
2018-09-24T20:32:53Z (6 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+304 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180924A (trigger #863186)
(Ukwata, et al., GCN Circ. 23261).  The BAT ground-calculated position is
RA, Dec = 49.207, -58.524 deg, which is 
   RA(J2000)  =  03h 16m 49.7s 
   Dec(J2000) = -58d 31' 27.6" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows a couple peaks starting at ~T-90 sec,
peaking at ~T=50 and ~T0 sec, and returning to baseline ~T+30 sec.
T90 (15-350 keV) is 95.1 +- 10.9 sec (estimated error including systematics).
 
The time-averaged spectrum from T-85.15 to T+26.35 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.94 +- 0.14.  The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.73 sec in the 15-150 keV band
is 0.6 +- 0.1 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/863186/BA/
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