GCN Circular 3581

A. Falcone (PSU), D. Palmer (LANL), A. Blustin (MSSL), S. Barthelmy
(GSFC), J. Cummings (GSFC/NRC), H. Krimm (GSFC/USRA), D. Burrows, D.
Morris, C. Gronwall (PSU), C. Markwardt (GSFC/UMD), K. Page
(Leicester), N. Gehrels (GSFC)

At 04:29:02.39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located on-board GRB050713 (trigger=145675).  The spacecraft slewed
immediately and was on target at approximately 70 seconds. The
flight-determined location is RA,Dec 320.536,+77.072 {+21h 22m 09s, +77d
04' 20"} (J2000) with an uncertainty of 3 arcmin (radius, stat+sys).
This is a bright burst with a peak count rate of 6000 cts/sec in the
15-350 keV band.  The brightest part of the burst duration is ~20
seconds, followed by smaller peaks at T+50, T+65 and T+105 seconds.

The spacecraft slewed immediately and the XRT began observing the burst
at 04:30:14.9 UT (72.6 s after the BAT trigger).  XRT found a very
bright, uncataloged, fading X-ray source at:

RA:   +21h 22m 09.6s (J2000),
DEC: +77d 04' 30.3" (J2000).

This position is 11 arcseconds from the BAT position.  The estimated
uncertainty is 6 arcseconds radius (90% containment).

The Swift Ultra Violet/Optical Telescope (UVOT) observations began at
04:30:17.7 UT, 75 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 125 sec after the BAT trigger.
Based on comparisons to the DSS and USNO, we detect no new source at the
XRT position. The 3-sigma upper limit in the V-filter is approximately
17.81 mag.