GCN Circular 11799

R. Margutti (INAF-OAB), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
S. Campana (INAF-OAB), P. D'Avanzo (INAF-OAB),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), C. Gronwall (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), O. M. Littlejohns (U Leicester),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/IASFPA),
M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.) and
C. A. Swenson (PSU) report on behalf of the Swift Team:

At 15:27:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110318B (trigger=449549).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 211.695, -51.559, which is 
   RA(J2000)  =  14h 06m 47s
   Dec(J2000) = -51d 33' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a couple peaks
with a total duration of about 10 sec.  The peak count rate
was ~1100 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 15:28:22.5 UT, 72.8 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 211.67805, -51.57933 which
is equivalent to:
   RA(J2000)  = 14h 06m 42.73s
   Dec(J2000) = -51d 34' 45.6"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 82 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 consistent with the Galactic value of 2.42
x 10^21 cm^-2 (Kalberla et al. 2005). 

The UVOT processed images are delayed and will be analyzed as soon as
possible. 

Burst Advocate for this burst is R. Margutti (raffaella.margutti AT brera.inaf.it). 
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.)