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GCN Circular 32892

Subject
GRB 221027B: Swift-BAT refined analysis
Date
2022-10-30T16:03:48Z (2 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), D. M. Palmer (LANL),
T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU),
M. Stamatikos (OSU) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 221027B (trigger #1131397)
(Lien et al., GCN Circ. 32867).  The BAT ground-calculated position is
RA, Dec = 225.601, 47.451 deg which is
   RA(J2000)  =  15h 02m 24.2s
   Dec(J2000) = +47d 27' 04.4"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 45%.

The mask-weighted light curve shows a structure with two pulses that start
at ~T-6 s and end at ~T+4 s. The first weaker peak occurs at ~T-5 s,
followed by the main peak that occurs at ~T0. T90 (15-350 keV)
is 8.66 +- 1.10 sec (estimated error including systematics).

The time-averaged spectrum from T-5.98 to T+4.20 sec is best fit
by a simple power-law model.  The power law index of the
time-averaged spectrum is 2.39 +- 0.19.  The fluence in
the 15-150 keV band is 5.8 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak
photon flux measured from T-0.08 sec in the 15-150 keV band
is 3.4 +- 0.4 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/1131397/BA/
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