GRB 240820***A***: Swift-BAT refined analysis
 
<somebody goes first>
<add the BA alphabetically>
S. D. Barthelmy (GSFC), 
R. Gupta (GSFC),
H. A. Krimm (NSF),
S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC),
M. J. Moss (GSFC),
D. M. Palmer (LANL),
T. Parsotan (GSFC),
D. Sadaula (GSFC/UMBC),
T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240820***A*** (trigger #1249653)
(NAME, et al., GCN Circ. xxxx).  The BAT ground-calculated position is
RA, Dec = 280.344, -4.935 deg which is 
   RA(J2000)  =  18h 41m 22.5s 
   Dec(J2000) = -04d 56' 07.6" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 91%.
 
[Description about the mask-weighted light curve]
T90 (15-350 keV) is 0.34 +- 0.02 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.00 to T+0.42 sec fit by a simple
power-law model shows the power law index of 2.85 +- 0.09 (chi squared 89.43 for 57 d.o.f.).
The fluence in the 15-150 keV band is 3.1 +- 0.1 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band
is 6.9 +- 0.4 ph/cm2/sec.
 
A single blackbody fit to the time-averaged spectrum shows the blackbody
temperature of 7.41 +- 0.32 keV (chi squared 95.74 for 57 d.o.f.).
A thermal bremsstrahlung model fit shows the temperature of 26.25 +- 2.22 keV
(chi squared 55.17 for 57 d.o.f.).  A double blackbody fit shows the lower temperature
of 5.85 +0.49 keV and the higher temperature of 15.50 +4.22 keV
(chi squared 49.31 for 55 d.o.f.).  All the quoted errors are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1249653