GCN Circular 19478

D. Kocevski (NASA/GSFC/ORAU), P.A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), B. Mingo (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. G. R. Roegiers (PSU)
and M. H. Siegel (PSU) report on behalf of the Swift Team:

At 14:43:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160601A (trigger=688452).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 235.034, +64.495 which is 
   RA(J2000) = 15h 40m 08s
   Dec(J2000) = +64d 29' 41"
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 0.2 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 14:44:16.3 UT, 74.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 234.9351, 64.5401 which
is equivalent to:
   RA(J2000)  = 15h 39m 44.43s
   Dec(J2000) = +64d 32' 24.2"
with an uncertainty of 3.3 arcseconds (radius, 90% containment). This
location is 223 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. This position is more than
2-sigma away from the BAT position, and so possibly unrelated to the
trigger. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.04
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 250 seconds with the U filter
starting 78 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 none of
the XRT error circle. 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. 

Burst Advocate for this burst is D. Kocevski (dankocevski AT gmail.com). 
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.)