GCN Circular 7147

T. Sakamoto (NASA/UMBC), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), M. M. Chester (PSU),
S. D. Hunsberger (PSU), K. L. Page (U Leicester),
J. L. Racusin (PSU), P. Romano (Univ. Bicocca & INAF-OAB),
G. Sato (GSFC/ISAS), B. Sbarufatti (INAF-IASFPA),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
E. Troja (INAF-IASFPA) and D. E. Vanden Berk (PSU) report on behalf
of the Swift Team:

At 20:13:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071227 (trigger=299787).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 58.120, -55.953 which is 
   RA(J2000) = 03h 52m 29s
   Dec(J2000) = -55d 57' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed at least three 
spikes with a duration of about 5 sec.  The peak count rate
was ~4500 counts/sec (15-350 keV), at ~0.5 sec after the trigger. 

The XRT began observing the field at 20:15:06 UT, 79 seconds after the
BAT trigger. From prompt downlinked data, XRT found a  variable, uncatalogued 
X-ray source located at RA, Dec 58.1316, -55.9833 which is
   RA(J2000)  =  03h 52h 31.58s
   Dec(J2000) = -55d 58' 59.9"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). 
This location is 112 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 9.6e-10 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 86 seconds after the BAT trigger, and a
second finding chart of 400 seconds in V starting 192 seconds after
the 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. The 3-sigma upper limit at the XRT position is 19.9 mag in
White, 19.0 in V. 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
extinction corresponding to E(B-V) = 0.01. 

Burst Advocate for this burst is T. Sakamoto (takanori 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.)