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GCN Circular 12612

Subject
GRB 111204A: Swift detection of a burst
Date
2011-12-04T13:50:44Z (12 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Sonbas (GSFC/USRA/Adiyaman Univ.), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
S. Campana (INAF-OAB), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU),
C. A. Swenson (PSU) and T. N. Ukwatta (MSU) report on behalf of the
Swift Team:

At 13:37:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 111204A (trigger=509018).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 336.641, -31.395 which is 
   RA(J2000) = 22h 26m 34s
   Dec(J2000) = -31d 23' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 80 sec.  The peak count rate
was ~400 counts/sec (15-350 keV), at ~50 sec after the trigger. 

The XRT began observing the field at 13:40:08.0 UT, 159.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 336.62912, -31.37514 which is
equivalent to:
   RA(J2000)  = 22h 26m 30.99s
   Dec(J2000) = -31d 22' 30.5"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 80 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 1.08
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 143 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 34% 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
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
0.01. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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.)

[GCN OPS NOTE(04dec11): Per author's request, the contact address for ES
has been changed to edasonbas@yahoo.com .]
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