Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 32998

GRB 221201A: Swift detection of a burst
2022-12-01T12:47:26Z (2 years ago)
Phil Evans at U of Leicester <>
E. Troja (NASA/GSFC/UMCP), M. G. Bernardini (INAF-OAB),
R. Brivio (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU),
P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester),
M. Ferro (INAF-OAB), J.D. Gropp (PSU), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
K. L. Page (U Leicester), D. M. Palmer (LANL),
C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 12:25:05 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 221201A (trigger=1142847).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 266.933, -68.260 which is 
   RA(J2000) = 17h 47m 44s
   Dec(J2000) = -68d 15' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
structure with a duration of about 40 sec.  The peak count rate 
was ~5000 counts/sec (15-350 keV), at ~-13 sec after the trigger. 
(The peak occurred during a pre-planned slew and the nominal trigger
time is the start of the first post-slew image.)

The XRT began observing the field at 12:27:56.2 UT, 170.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 266.9228, -68.2510 which is equivalent to:
   RA(J2000)  = 17h 47m 41.47s
   Dec(J2000) = -68d 15' 03.6"
with an uncertainty of 5.7 arcseconds (radius, 90% containment). This
location is 35 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 0.1 s image was 2.34e-08 erg cm^-2 s^-1 (0.2-10

UVOT took a finding chart exposure of 202 seconds with the U filter starting
337 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 19.2 mag. Data
from the list of sources generated on-board are not available at this time. No
correction has been made for the expected extinction corresponding to E(B-V) of

Burst Advocate for this burst is E. Troja (nora.gsfc 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:
Looking for U.S. government information and services? Visit