GCN Circular 13588

E. Troja (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU), S. T. Holland (STScI),
J. A. Kennea (PSU), O. M. Littlejohns (U Leicester),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 21:28:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120805A (trigger=530031).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 216.533, +5.802 which is 
   RA(J2000) = 14h 26m 08s
   Dec(J2000) = +05d 48' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 50 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 21:30:13.0 UT, 123.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 216.54056, 5.82571 which is equivalent
to:
   RA(J2000)  = 14h 26m 09.73s
   Dec(J2000) = +05d 49' 32.6"
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This
location is 89 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 2.22
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of  90 seconds with the White filter
starting 126 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. 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 0.03. 

Burst Advocate for this burst is E. Troja (eleonora.troja 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.)