GCN Circular 3839

M. Page (UCL-MSSL), D. Palmer (LANL), S. Barthelmy (GSFC),
D. Burrows (PSU), A. Beardmore (U. Leicester). J. Kennea (PSU),
M. Chester (PSU), and T. Sakamoto (GSFC/NRC)
on behalf of the Swift team report

At 23:50:27 BAT triggered and located GRB050820B (Trigger= 151334)
at RA,Dec=135.557d, -72.668d {+09h 02m 14s, -72d 40' 03"} (J2000)
with an uncertainty of 2 arcmin (radius, 90% containment, stat+sys).
The BAT lightcurve shows 20 seconds of emission with a shorter
softer peak at T+2 seconds, and a broader, brighter, harder
interval of emission from T+6 to T+14s.  The peak count rate
is 10,000 counts/s (15-350 keV) at T+9s.  The first peak has
a maximum count rate of 2000 counts/s, with no obvious
emission above 100 keV.

Due to Earth limb constraints, the Swift slew is delayed until
until 00:16 UT (T+26 minutes).