GCN Circular 15099

M. Stamatikos (OSU/NASA/GSFC), P. D'Avanzo (INAF-OAB),
M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the
Swift Team:

At 04:53:38 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130816B (trigger=566561).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 170.093, -57.558 which is 
   RA(J2000) = 11h 20m 22s
   Dec(J2000) = -57d 33' 28"
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 20 sec.  The peak count rate
was ~2440 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 04:54:48.8 UT, 70.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 170.01845, -57.55829 which is
equivalent to:
   RA(J2000)  = 11h 20m 04.43s
   Dec(J2000) = -57d 33' 29.8"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 143 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.  We cannot determine whether the source is
fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 4.04
x 10^21 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 75 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 none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. Because of the density of
catalogued stars, further analysis is required to report an upper limit for any
afterglow in the region. No correction has been made for the large, but
uncertain extinction expected. 

Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 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.)