GRB 180418***A***, Swift-BAT refined analysis
 
<somebody goes first>
<add the BA alphabetically>
S. D. Barthelmy (GSFC), 
J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC),
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 180418***A*** (trigger #826428)
(NAME, et al., GCN Circ. xxxx).  The BAT ground-calculated position is
RA, Dec = 170.129, 24.927 deg which is 
   RA(J2000)  =  11h 20m 30.9s 
   Dec(J2000) = +24d 55' 37.3" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
[Description about the mask-weighted light curve]
T90 (15-350 keV) is 4.4 +- 2.5 sec (estimated error including systematics).
 
The time-averaged spectrum from T+0.1 to T+7.2 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.34 +- 0.74, 
and Epeak of 79.7 +- 39.4 keV (chi squared 55.16 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.1 +- 0.4 x 10^-07 erg/cm2
and the 1-sec peak flux measured from T+0.24 sec in the 15-150 keV band is
3.0 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.36 +- 0.14 (chi squared 62.17 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/826428/BA/