TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2890
SUBJECT: GRB041220:  Swift-BAT burst
DATE:    04/12/21 02:48:49 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott@lheamail.gsfc.nasa.gov>

H. Krimm (GSFC/USRA), L. Angelini (GSFC/JHU), L. Barbier (GSFC),
S. Barthelmy (GSFC), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC),
M. Goad (U.Leicester), D. Hullinger (GSFC/UMD), C. Markwardt (GSFC/UMD),
K. McLean (LANL/UTD), D. Palmer (LANL), A. Parsons (GSFC),
P. Roming (PSU), G. Sato (ISAS), M. Suzuki (Saitama), T. Takashima (ISAS),
J. Tueller (GSFC)  on behalf of the Swift BAT team:

At 22:58:26 UT, the Swift-BAT triggered and located on-board GRB041220
(BAT Trigger #100433).  The spacecraft did not autonomously slew
to the burst since automated slewing is not yet enabled.  Automated
notification to the BAT Team through TDRSS was partially enabled
for this burst.

The ground-calculated location is RA, DEC 291.286, +60.624 (J2000)
with an uncertainty of 12 arcmin (radius, dominated by a large systematic
uncertainty due to the lack of an on-orbit boresight alignment calibration).
This is ~16 degrees off the BAT boresight.  It was imaged at >22 sigma.
The source is 19 degrees off the galactic plane.

The burst is a fast-rise exponential-decay (FRED) with a full-width
at half-max of ~2 sec.  There is some indication of emission out
to 18 sec after the peak.  The peak flux was 2.2 events/cm^2/sec
in the 15-350 keV band (~8 Crab).  The total fluence is
approximately 5.9 events/cm^2 (15-350 keV), or 1E-6 erg/cm^2.