GCN Circular 15986

S. B. Cenko (GSFC), M. G. Bernardini (INAF-OAB), D. N. Burrows (PSU),
P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), T. Sakamoto (AGU),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 00:09:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140318A (trigger=592204).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 184.053, +20.207 which is 
   RA(J2000) = 12h 16m 13s
   Dec(J2000) = +20d 12' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak 
structure with a duration of about 30 sec.  The peak count rate
was ~1320 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 00:11:12.7 UT, 124.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 184.0906, 20.2080 which is equivalent to:
   RA(J2000)  = +12h 16m 21.74s
   Dec(J2000) = +20d 12' 28.8"
with an uncertainty of 6.9 arcseconds (radius, 90% containment). This
location is 127 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 3.63e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 132 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. Results from the 2.7'x2.7' sub-image
are not available at this time. 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 0.02. 

Burst Advocate for this burst is S. B. Cenko (brad.cenko 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.)