GCN Circular 13822

A. Maselli (INAF-IASFPA), W. H. Baumgartner (GSFC/UMBC),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC),
S. T. Holland (STScI), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC) and
F. E. Marshall (NASA/GSFC) report on behalf of the Swift Team:

At 22:40:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120927A (trigger=534815).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 136.600, +0.417 which is 
   RA(J2000) = 09h 06m 24s
   Dec(J2000) = +00d 25' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a broad single-peaked
structure with a duration of about 50 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 22:43:20.0 UT, 154 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 136.614125, 0.415722 which is equivalent
to:
   RA(J2000)  = 09h 06m 27.20s
   Dec(J2000) = +00d 24' 56.6"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 52 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. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 158 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
BAT and XRT error circles. 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
0.04. 

Burst Advocate for this burst is A. Maselli (maselli AT ifc.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.)