GCN Circular 4297

M.Ohno, T.Takahashi, Y.Fukazawa (Hiroshima U.), 
K.Yamaoka, S.Sugita (Aoyama Gakuin U.),
Y.Terada (RIKEN), K.Abe, Y.Endo, S.Hong, K.Onda,
M.Tashiro (Saitama U.), K.Nakazawa, G.Sato,
T.Takahashi (ISAS/JAXA), R.Miyawaki,
M.Kokubun, K.Makishima (Univ. of Tokyo) and the HXD-II team

  The GRB 051008 prompt emission (Swift-BAT trigger #158855; 
Marshall et al., GCN 4069
Not found
 
 
, Parsons et al., GCN 4075
Not found
 
 
, Barthelmy et al.,
GCN 4077
Not found
 
 
) triggered Suzaku Wideband All-sky Monitor (WAM), 
which covers an energy band of 50 keV - 5 MeV at 16:33:18 UT. 

The light curve shows two peaks with total duration about 48.2 sec. 
This is consistent with Swift observation (GCN4069
Not found
 
 
). 

We performed the time-averaged spectral analysis 
using the position information provided by Swift (Marshall et al., GCN 4069
Not found
 
 
). 
We found that the emission extends up to at least 2 MeV. 
The cutoff power law model provided a good fit. 
In the preliminary results, the photon index was 1.24 (+0.13 -0.15) 
and the cutoff energy was 1535 (+1419 -561) keV.  
The peak flux on 1 sec time scale was 4.1 (+0.3 -0.3) photons/s/cm^2 
(100 keV - 2 MeV) and the fluence was 3.2 (+0.2 -0.2)e-5 erg/cm^2
(100 keV - 2 MeV). The errors are at the statistical 90 % confidence level.
Systematic errors, such as the flux calibration uncertainties of
about 20%, are not included in the errors.

You can see the detail information about the instrument of WAM and
the lightcurve in the Web site

http://www.astro.isas.ac.jp/suzaku/research/HXD-WAM/WAM-GRB/grb/grb_table.html

Further analysis and the refinement is in progress.