TITLE:   GCN CIRCULAR
NUMBER:  31288
SUBJECT: GRB 211223C: Swift detection of a burst
DATE:    21/12/23 14:39:35 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

P. A. Evans (U Leicester), S. D. Barthelmy (GSFC),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (PSU) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 14:29:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 211223C (trigger=1090656).  Swift did not slew to the burst
due to a pointing constraint.  The BAT on-board calculated location is 
RA, Dec 227.164, -26.873 which is 
   RA(J2000) = 15h 08m 39s
   Dec(J2000) = -26d 52' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 20 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 23:31 UT on 2021 December 29. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is P. A. Evans (pae9 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/)