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GCN Circular 20210

Subject
GRB 161129A: Swift detection of a burst
Date
2016-11-29T07:32:25Z (7 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
D. Kocevski (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), B. Mingo (U Leicester),
K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 07:11:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161129A (trigger=724438).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 316.193, +32.125 which is 
   RA(J2000)  =  21h 04m 46s
   Dec(J2000) = +32d 07' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
with a duration of about 50 sec.  The peak count rate
was ~4400 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:13:01.8 UT, 82.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 316.22890, 32.13574 which is equivalent
to:
   RA(J2000)  = 21h 04m 54.94s
   Dec(J2000) = +32d 08' 08.7"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 116 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.50 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.5
(+2.84/-2.37) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White 
filter  starting 86 seconds after the BAT trigger. No credible 
afterglow candidate has  been found in the initial data products. The 
2.7'x2.7' sub-image does not cover 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 0.21. 

Burst Advocate for this burst is D. Kocevski (dankocevski 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.)
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