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GCN Circular 28408

Subject
GRB 200909B: Swift-BAT refined analysis
Date
2020-09-10T12:14:36Z (4 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
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 200909B (trigger #995288)
(Melandri, et al., GCN Circ. 28406).  The BAT ground-calculated position is
RA, Dec = 175.171, -31.199 deg which is
    RA(J2000)  =  11h 40m 41.1s
    Dec(J2000) = -31d 11' 54.7"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 35%.
  
The mask-weighted light curve shows a single peak that stars at T-6 sec,
peaks at T+1 sec, and ends at T+20 sec.  A hint of an extended emission
is visible until T+40 sec.  T90 (15-350 keV) is 16.9 +- 2.2 sec (estimated error
including systematics).
  
The time-averaged spectrum from T-5.6 to T+14.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.60 +- 0.14.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band
is 1.3 +- 0.3 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/995288/BA/
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