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GCN Circular 23213

Subject
GRB 180905A, Swift-BAT refined analysis
Date
2018-09-06T16:12:08Z (6 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), V. D'Elia (SSDC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+250 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180905A (trigger #859421)
(D'Elia et al., GCN Circ. 23201).  The BAT ground-calculated position is
RA, Dec = 91.038, -4.592 deg which is
  RA(J2000)  =  06h 04m 09.2s
  Dec(J2000) = -04d 35' 31.9"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 29%.

The mask-weighted light curve shows a weak long pulse that starts
at ~T-60 s and ends at ~T+150 s. Note that the burst came into the BAT
field of view at T-84 s, and BAT entered the SAA after ~ T+250 s. Therefore,
there might be additional burst emission before and after the available event
data range. T90 (15-350 keV) is 165.3 +- 28.9 sec (estimated error including
systematics).

The time-averaged spectrum from T-58.9 to T+146.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.60 +- 0.12.  The fluence in the 15-150 keV band is 4.2 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-2.09 sec in the 15-150 keV band
is 1.0 +- 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/859421/BA/
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