TITLE:   GCN CIRCULAR
NUMBER:  15699
SUBJECT: GRB 140108A: Swift detection of a burst
DATE:    14/01/08 17:29:05 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB),
J. A. Kennea (PSU), A. Melandri (INAF-OAB), D. M. Palmer (LANL),
M. H. Siegel (PSU), E. Sonbas (NASA/GSFC/Adiyaman Univ.),
E. Troja (NASA/GSFC/UMCP) and T. N. Ukwatta (MSU) report on behalf of
the Swift Team:

At 17:18:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140108A (trigger=583338).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 325.178, +58.766 which is 
   RA(J2000)  =  21h 40m 43s
   Dec(J2000) = +58d 45' 58"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several peaks at
T+5, T+35, and T+85 sec with a total duration of about 120 sec.  
The peak count rate was ~8000 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 17:19:51.1 UT, 68.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 325.1106, 58.7437 which is equivalent to:
   RA(J2000)  = +21h 40m 26.54s
   Dec(J2000) = +58d 44' 37.3"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 149 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 3.34e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White 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 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 large, but uncertain extinction expected. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin AT 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.)