TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4297 SUBJECT: GRB051008: Suzaku WAM observation of the prompt emission DATE: 05/11/22 12:06:55 GMT FROM: Masanori Ohno at Hiroshima U 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, Parsons et al., GCN 4075, Barthelmy et al., GCN 4077) 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). We performed the time-averaged spectral analysis using the position information provided by Swift (Marshall et al., GCN 4069). 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.