TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4135
SUBJECT: GRB 051021B:  Refined analysis of the Swift-BAT burst
DATE:    05/10/22 15:52:56 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott@lheamail.gsfc.nasa.gov>

S. Barthelmy (GSFC), L. Barbier (GSFC), P. Boyd (GSFC-UMBC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), 
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC), W. Voges (MPE) 
on behalf of the Swift-BAT team:

Using the full data set from the recent telemetry downlink, we report
further analysis of Swift-BAT GRB 051021B (trigger #160672)
(Retter, et al., GCN 4126).  The ground-analysis position is
RA,Dec 126.059,-45.537 {8h 24m 14.2s,-45d 32' 13.0"} (J2000)
with an uncertainty of 1.3 arcmin (radius, 90%, stat+sys).
T90 is 47 +- 3 sec.  The partial coding fraction is 88 %.
The lightcurve has single FRED peak starting at T-6 sec (FWHM of ~12 sec)
with the decay extending out to greater than T+20 sec.  There is
a second, smaller peak at ~T+20.  Fitting a simple power law over
the full interval from T-5.5 to T+51.5 sec, the photon index is
1.52 +/- 0.14 with a fluence of 9.1 +/- 0.8 X 10^-7 erg/cm^2.
The peak flux in a 1-sec wide window starting at T-2.5 sec
is 0.63 +/- 0.13 ph/cm^2/sec.  All values are in the 15-150 keV band
at the 90% confidence level.