GCN Circular 15578

T. N. Ukwatta (MSU), V. D'Elia (ASDC), C. B. Markwardt (NASA/GSFC),
A. Melandri (INAF-OAB), K. L. Page (U Leicester) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 09:18:38 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131205A (trigger=580267).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 131.609, -60.174 which is 
   RA(J2000) = 08h 46m 26s
   Dec(J2000) = -60d 10' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiple peaked
structure with a duration of about 60 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:20:07.5 UT, 88.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 131.6276, -60.1556
which is equivalent to:
   RA(J2000)  = 08h 46m 30.63s
   Dec(J2000) = -60d 09' 20.0"
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This
location is 74 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 1.50
x 10^21 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 93 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. 
Data from the list of sources generated on-board are not available at this
time. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.26. 

We note that the spacecraft star tracker was out of lock during a 
portion of this GRB, but we believe the burst is real. The position
may be revised after further processing. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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.)