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GCN Circular 34938

Subject
GRB 231104A: Swift detection of a bright burst
Date
2023-11-04T02:34:58Z (7 months ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email

K. L. Page (U Leicester), J.D. Gropp (PSU), D. M. Palmer (LANL) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:47:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 231104A (trigger=1194500).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 23.789, +83.791 which is 
   RA(J2000) = 01h 35m 09s
   Dec(J2000) = +83d 47' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The available BAT light curve (up to T+8s)
showed a complex structure with a duration of at least 12 sec. 
The peak count rate was ~50,000 counts/sec (15-350 keV), 
at ~0 sec after the trigger. 

The XRT began observing the field at 01:49:10 UT, 90.2 seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with an enhanced position: RA, Dec 23.8113,
83.7912 which is equivalent to:
   RA(J2000)  = 01h 35m 14.7s
   Dec(J2000) = +83d 47' 28"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 9 arcseconds from the BAT onboard position. This position
may be improved as more data are received; the latest position is
available at https://www.swift.ac.uk/sper. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 860 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 25% of
the BAT 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
BAT 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
0.157. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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/)


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