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GCN Circular 20179

Subject
GRB 161117A: Swift detection of a burst with an optical counterpart
Date
2016-11-17T01:46:55Z (8 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), V. D'Elia (ASDC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/NSF/USRA), F. E. Marshall (NASA/GSFC) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 01:35:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161117A (trigger=722604).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 322.070, -29.629 which is 
   RA(J2000)  =  21h 28m 17s
   Dec(J2000) = -29d 37' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several bright peaks
with a total duration of about 160 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~110 sec after the trigger. 

The XRT began observing the field at 01:36:37.5 UT, 60.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 322.0530, -29.6119 which is equivalent to:
   RA(J2000)  = +21h 28m 12.72s
   Dec(J2000) = -29d 36' 42.8"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 81 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 8.04e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 69 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	21:28:12.53 = 322.05219
  DEC(J2000) = -29:36:48.9  = -29.61358
with a 90%-confidence error radius of about 0.62 arc sec. This position is 6.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.40 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.06. 

Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.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.)
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