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GCN Circular 23769

Subject
GRB 190123A: Swift detection of a burst
Date
2019-01-23T12:32:59Z (5 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
A. D'Ai (INAF-IASFPA), D. N. Burrows (PSU), J.D. Gropp (PSU),
N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 12:19:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190123A (trigger=885314).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 53.229, +45.484 which is 
   RA(J2000) = 03h 32m 55s
   Dec(J2000) = +45d 29' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~1400 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 12:21:10.4 UT, 117.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 53.22071, 45.52425 which
is equivalent to:
   RA(J2000)  = 03h 32m 52.97s
   Dec(J2000) = +45d 31' 27.3"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 146 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 2.5 s image was 7.12e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 125 seconds with the White filter
starting 124 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. 
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 extinction. 

Burst Advocate for this burst is A. D'Ai (antonino.dai 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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