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GCN Circular 32537

Subject
GRB 220907A: Swift-BAT refined analysis
Date
2022-09-08T20:58:07Z (2 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC),  H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC),
T. Sakamoto (AGU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 220907A (trigger #1123129)
(Page, et al., GCN Circ.32526).  The BAT ground-calculated position is
RA, Dec = 268.869, -20.303 deg which is
   RA(J2000)  =  17h 55m 28.6s
   Dec(J2000) = -20d 18' 10.8"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.
The mask-weighted light curve shows a single peak of ten seconds approximate
duration starting at T-1 sec.   A spacecraft maneuver took the source out of the BAT
field of view at approximately 400 seconds.  T90 (15-350 keV) is 8.49 +- 1.56 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.60 to T+10.29 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.99 +- 0.24.  The fluence in the 15-150 keV band is 4.1 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.70 sec in the 15-150 keV band
is 1.0 +- 0.2 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/1123129/BA/
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