[vsnet-grb-info 8337] Swift Trigger 361477, called GRB090831B, is probably not real.
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Tue Sep 1 21:45:10 JST 2009
TITLE: GCN CIRCULAR
NUMBER: 9860
SUBJECT: Swift Trigger 361477, called GRB090831B, is probably not real.
DATE: 09/09/01 12:45:04 GMT
FROM: Massimiliano de Pasquale at MSSL-UCL <mdp at mssl.ucl.ac.uk>
J.R. Cummings (NASA/UMBC), P.A. Evans (U. Leicester), J.A. Kennea (PSU),
C. Pagani (PSU), and M. De Pasquale (MSSL/UCL) on behalf of the Swift
team report:
The ground analysis of BAT data from trigger 361477 (De Pasquale et al.,
GCN Circ. 9851) shows a very weak excess in the low energy bands only.
The response is consistent with a somewhat unusually large noise
fluctuation in the image domain caused by the presence of a bright source
in the BAT partially coded field of view (Cyg-X1).
The XRT observed the field for 3.23 ks between T0+150 s and T0+10 ks. The
data are entirely in Photon Counting mode. We do not find any source in
the field of view. A 3-sigma upper limit on covering the BAT onboard error
circle is 2.7 x 10^-3 ct/sec.
No new source is found in the UVOT white filter finding chart (153-303s
after the trigger) inside the BAT error circle down to a 3 sigma upper
limit of 20.9.
We conclude that the trigger is unlikely to be due to a GRB or any other
astrophysical source.
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