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GCN Circular 23413

Subject
GRB 181110A: Swift detection of a burst with an optical counterpart
Date
2018-11-10T08:59:09Z (6 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
P. A. Evans (U Leicester), K. L. Page (U Leicester) and
T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 08:43:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 181110A (trigger=871316).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 302.342, -36.903 which is 
   RA(J2000) = 20h 09m 22s
   Dec(J2000) = -36d 54' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 150 sec.  The peak count rate
was ~3870 counts/sec (15-350 keV), at ~10 sec after the trigger. 

The XRT began observing the field at 08:44:35.2 UT, 64.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 302.31711, -36.89632 which
is equivalent to:
   RA(J2000)  = 20h 09m 16.11s
   Dec(J2000) = -36d 53' 46.8"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 75 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 0.1 s image was 5.82e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 72 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	20:09:16.28 = 302.31782
  DEC(J2000) = -36:53:47.8  = -36.89661
with a 90%-confidence error radius of about 0.63 arc sec. This position is 3.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.39 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.07. 

Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 
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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