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GCN Circular 33067

GRB 221216A: Swift detection of a burst
2022-12-16T11:34:25Z (a year ago)
Kim Page at U.of Leicester <>
S. Dichiara (PSU), R. A. J. Eyles-Ferris (U Leicester),
J.D. Gropp (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 11:21:20 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 221216A (trigger=1144698).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 326.021, -34.405 which is 
   RA(J2000) = 21h 44m 05s
   Dec(J2000) = -34d 24' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of at least 200 sec.  The peak count rate
was ~1640 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:22:32.6 UT, 71.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 326.0326, -34.4223 which is equivalent to:
   RA(J2000)  = 21h 44m 7.82s
   Dec(J2000) = -34d 25' 20.3"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 81 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 the expected extinction corresponding to E(B-V) of

Burst Advocate for this burst is S. Dichiara (simonedichiara55 AT 
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:
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