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GCN Circular 9740

Subject
Swift-BAT trigger 358760 is most likely not a GRB
Date
2009-07-31T17:30:56Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
B. Sbarufatti (INAF-IASFPA), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of trigger #358760 (Subrufatti, et al., GCN Circ. 9739).
The BAT ground-calculated position is RA, Dec = 189.693, -15.363 deg,
with an uncertainty of 3.3 arcmin, (radius, sys+stat, 90% containment).
This is 2.7 arcmin from the flight position.  The partial coding was 100%.
This is only a 5.5 sigma detection in the image domain.  The mask-weighted
lightcurve shows a very marginal detection in the 25-100 keV band in a single
64 msec time bin and nothing in the other two energy bands.  There is also
a weak cosmic ray shower during this 64-msec bin.  Given this very maginal
evidence, we do not think this trigger is due to a GRB.  It is very
probably a noise fluctution coupled with a weak CR Shower. However, we can not
rule out a GRB origin.
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