GCN Circular 7713

H. A. Krimm (CRESST/GSFC/USRA), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
O. Godet (U Leicester), C. Guidorzi (INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
J. A. Kennea (PSU), V. La Parola (INAF-IASFPA),
P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Romano (INAF-IASFPA),
B. Sbarufatti (INAF-IASFPA), R. L. C. Starling (U Leicester),
E. Troja (U Leicester/INAF-IASFPA), L. Vetere (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 10:32:37 UT, the Swift Burst Alert Telescope (BAT) triggered (trigger=311603)
and located an X-ray source.  Swift slewed immediately to this location. 
It is also possible that it was a false (noise) event in the BAT.  
The BAT on-board calculated location is RA, Dec 263.833, -35.623 which is 
   RA(J2000) = 17h 35m 20s
   Dec(J2000) = -35d 37' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with image triggers, there is 
not much information in the  BAT light curve.  The peak count rate
was ~300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 10:35:01.4 UT, 144.2 seconds after
the BAT trigger. Just inside the BAT error circle (172 arcseconds from the 
BAT onboard position), the XRT detected a possible source, coincident with 
a ROSAT source 1RXH J173523.7-354013

UVOT took a finding chart exposure of  78 seconds with the White
(160-650 nm)  filter starting 154 seconds after the BAT trigger. No
afterglow candidate has  been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of  the XRT error circle. Because of
the density of catalogued stars, further  analysis is required to
report an upper limit for any afterglow in the  sub-image. The 8'x8'
region for the list of sources generated on-board covers  100% of the
XRT error circle.  No correction has been made for the large, but
uncertain extinction  expected. 

Given the information available, it is possible that this event is due
to noise.  The BAT triggered on the rising edge of the SAA passage and
there is a possibility that the XRT events are due to cosmic rays.  In
any case, the spectrum and light curve tell us that this trigger is
NOT a GRB. 

Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)