TITLE:   GCN CIRCULAR
NUMBER:  22427
SUBJECT: Swift Trigger 811074: possible GRB 180221A
DATE:    18/02/21 06:50:00 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

M. Stamatikos (OSU/NASA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 06:30:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located possible GRB 180221A (trigger=811074).  Swift did not slew 
immediately due to an observational constraint. 
The BAT on-board calculated location is 
RA, Dec 326.772, -72.868 which is 
   RA(J2000) = 21h 47m 05s
   Dec(J2000) = -72d 52' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~2 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+43.6
minutes. There will be no XRT or UVOT data until this time. 

Due to the marginal significance of this event (7.01 sigma)
and the proximity of Swift to the SAA at the time of the
trigger, we cannot confirm that this is an actual GRB. 
Observations with XRT will help to determine the
nature of this event. 

Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT nasa.gov). 
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.)