[vsnet-grb-info 1733] GRB 050712: Swift detection of a weak burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3573
SUBJECT: GRB 050712: Swift detection of a weak burst
DATE:    05/07/12 15:04:45 GMT
FROM:    David Burrows at PSU/Swift  <dxb15 at psu.edu>

D. Grupe (PSU), S. Barthelmy (GSFC), J. Cummings, (GSFC/NRC),
H. Krimm (GSFC/USRA), C. Markwardt, (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC), D. Burrows, J. Nousek, A. Falcone, C. Gronwall (PSU),
T. Poole, A. Blustin (MSSL), and N. Gehrels (GSFC) on behalf of the Swift team:


At 14:00:27.51 UT, the Swift Burst Alert Telescope (BAT) triggered and located
on-board GRB050712 (trigger=145581).  The spacecraft slewed immediately.
The flight-determined location is RA,Dec 77.693,+64.899 {+05h 10m 46s,+64d 
53' 56"} (J2000) with an uncertainty of 3 arcmin (radius, stat+sys).  The 
burst lightcurve
has 4-5 peaks all within ~35 sec duration.  This is a weak burst with a peak
count rate of 500 cnts/sec in the 15-350 keV band.

This burst should not be confused with Trigger=145563 two hours earlier 
today.
Based on preliminary analysis, the BAT team believes the earlier trigger is 
not
a real GRB.


The XRT attempted to centroid on the afterglow at 14:03:14 UT (166 s after the
BAT trigger) but could not find a bright enough source for a successful 
on-board
centroid.  Ground analysis will be required to determine whether there is 
an X-ray
counterpart.

The Swift Ultra Violet/Optical (UVOT) observations began at 14:03:11.5 UT,
164 seconds after the BAT trigger.  The first data taken after the spacecraft
settled was a 100 sec exposure using the V filter with the midpoint of the
observation at 214 sec after the BAT trigger.  Based on comparisons to the
DSS, we detect no new source. The 5-sigma upper limit in the V-filter is 
17.94 mag.