TITLE:   GCN CIRCULAR
NUMBER:  31886
SUBJECT: GRB 220412B: Swift detection of a short burst
DATE:    22/04/12 17:26:32 GMT
FROM:    Jeffrey Gropp at PSU  <jdg44@psu.edu>

J.D. Gropp (PSU), S. Dichiara (PSU), J. A. Kennea (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), 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 17:06:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 220412B (trigger=1102329).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 320.794, -0.223 which is 
   RA(J2000) = 21h 23m 11s
   Dec(J2000) = -00d 13' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 0.5 sec.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 17:08:13.7 UT, 85.0 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

UVOT took a finding chart exposure of 130 seconds with the White filter
starting 89 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
0.060. 

Shortly after the BAT trigger, Swift entered the South Atlantic Anomaly which 
limited data collection for the first orbit. We are awaiting further observations. 

Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 
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/)