S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), H. A. Krimm (NSF),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210820A (trigger #1069551)
(Beardmore et al., GCN Circ. 30664). The BAT ground-calculated position is
RA, Dec = 20.622, 4.642 deg which is
RA(J2000) = 01h 22m 29.4s
Dec(J2000) = +04d 38' 30.6"
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
The mask-weighted light curve shows many weak overlapping pulses
that start at ~T0 and end at ~T+260 s. T90 (15-350 keV) is
196.8 +- 51.4 sec (estimated error including systematics).
The time-averaged spectrum from T+0.78 to T+258.97 sec is best fit by
a simple power-law model. The power law index of the time-averaged
spectrum is 2.26 +- 0.22. The fluence in the 15-150 keV band is
1.5 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+10.92 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at