GRB 110218***A***, Swift-BAT refined analysis
 
<somebody goes first>
<add the BA alphabetically>
S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL),
N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC),
D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS),
M. Stamatikos (OSU),
J. Tueller (GSFC),
T. N. Ukwatta (MSU)
(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 110218***A*** (trigger #445776)
(NAME, et al., GCN Circ. xxxx).  The BAT ground-calculated position is
RA, Dec = 280.296, -4.874 deg which is 
   RA(J2000)  =  18h 41m 11.1s 
   Dec(J2000) = -04d 52' 25.9" 
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
[Description about the mask-weighted light curve]
T90 (15-350 keV) is 0.0 +- 0.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T+0.0 to T+0.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
3.06 +- 0.52.  The fluence in the 15-150 keV band is 2.5 +- 0.8 x 10^-09 erg/cm2.
The 1-sec peak photon flux measured from T-0.00 sec in the 15-150 keV band
is 7.2 +- 2.3 ph/cm2/sec.  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/445776/BA/
 
We note that the fluence ratio in a simple power-law fit between the
25-50 keV band and the 50-100 keV band is 2.10.  This fluence ratio is larger
than 1.32 which can be achieved in the Band function of alpha=-1.0, beta=-2.5,
and Epeak=30 keV.  Thus, preliminary analysis shows that Epeak of the burst
is very likely around or below 30 keV.  Therefore the burst can be classified
as an X-ray flash (e.g. Sakamoto et al. 2008, ApJ, 679, 570).