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GCN Circular 6463

Subject
Swift trigger 280447 is probably a Galactic transient
Date
2007-05-26T09:37:03Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
G. Cusumano (INAF-IASFPA), V. Mangano (INAF-IASFPA),
P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester),
C. Pagani (PSU), D. M. Palmer (LANL),
P. Romano (Univ. Bicocca & INAF-OAB), B. Sbarufatti (INAF-IASFPA),
D. E. Vanden Berk (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf
of the Swift Team:

At 08:49:18 UT, the Swift Burst Alert Telescope (BAT) triggered (trigger=280447)
and located a probable Galactic transient.  Due to the Earth limb constraint,
the Swift slew to the target was delayed by 9 minutes. 
The BAT on-board calculated location is 
RA, Dec 301.271, +31.484 which is 
   RA(J2000)  =  20h 05m 05s
   Dec(J2000) = +31d 29' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for 64 second image triggers,
the raw BAT lightcurve available via TDRSS does not show any
obvious variation. 

The XRT began observing the field at 09:00:38 UT, 680 seconds after the
BAT trigger. XRT found a bright uncatalogued X-ray source
located at RA, Dec 301.3168, +31.3876 which is
   RA(J2000)  =  20h 05m 16.0s
   Dec(J2000) =  31d 23' 15.3"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 
This location is 374 arcseconds from the BAT on-board position,
outside the BAT error circle. The initial flux in the 2.5s image
was 8.8e-09 erg/cm2/s (0.2-10 keV). 

There is no UVOT information for this burst.  This trigger is
distinct and separate from the trigger 280450.  We will have a separate
circular on that second trigger shortly. 

This location is on the Galactic plane (lat=-0.2deg), the XRT intensity
is much brighter than would be expected for a GRB at T+10
minutes and is highly-absorbed non-power-law spectrum. 
Therefore this source is probably a Galactic transient.
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