GCN Circular 21308

P. A. Evans (U Leicester), D. N. Burrows (PSU),
A. Cholden-Brown (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Swift Team:

At 00:45:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170710A (trigger=761119).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 231.812, -38.547 which is 
   RA(J2000) = 15h 27m 15s
   Dec(J2000) = -38d 32' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 10 sec.  The peak count rate
was ~800 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 00:47:48.3 UT, 123.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 231.82076, -38.48434 which
is equivalent to:
   RA(J2000)  = 15h 27m 16.98s
   Dec(J2000) = -38d 29' 03.6"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 226 arcseconds from the BAT onboard position. This position
may be improved as more data are received; the latest position is
available at http://www.swift.ac.uk/sper.  We cannot determine whether
the source is fading at the present time. No spectrum from the promptly 
downlinked event data is yet available to determine the column density. 

The initial flux in the 2.5 s image was 4.07e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 131 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.17. 

Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 
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.)