GRB 240311***A***: Swift-BAT refined analysis
 
<somebody goes first>
<add the BA alphabetically>
S. D. Barthelmy (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),
T. Sakamoto (AGU)
(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 240311***A*** (trigger #1219546)
(NAME, et al., GCN Circ. xxxx).  The BAT ground-calculated position is
RA, Dec = 299.946, 34.530 deg which is 
   RA(J2000)  =  19h 59m 47.1s 
   Dec(J2000) = +34d 31' 49.2" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.
 
[Description about the mask-weighted light curve]
T90 (15-350 keV) is 648.62 +- 41.62 sec (estimated error including systematics).
 
The time-averaged spectrum from TTBD to TTBD sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.24 +- 0.22, 
and Epeak of 57.1 +- 5.2 keV (chi squared 58.84 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.5 +- 0.0 x 10^-05 erg/cm2
and the 1-sec peak flux measured from T+564.06 sec in the 15-150 keV band is
0.5 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.91 +- 0.05 (chi squared 88.60 for 57 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/1219546