GCN Circular 16842

R. L. C. Starling (U Leicester), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (NASA/GSFC), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 05:15:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140927A (trigger=613775).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 291.845, -65.388 which is 
   RA(J2000) = 19h 27m 23s
   Dec(J2000) = -65d 23' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a spiky
structure with a duration of about 30 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 05:17:13.7 UT, 122.3 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 291.79216, -65.39285 which is
equivalent to:
   RA(J2000)  = 19h 27m 10.12s
   Dec(J2000) = -65d 23' 34.3"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 81 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (7.56 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4
(+3.21/-2.72) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
123 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.08. 

Burst Advocate for this burst is R. L. C. Starling (rlcs1 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.)