TITLE: GCN CIRCULAR NUMBER: 6240 SUBJECT: GRB 070328: Suzaku WAM observation of the prompt emission DATE: 07/04/03 12:56:49 GMT FROM: Kazutaka Yamaoka at Aoyama Gakuin U S. Hong (Nihon U.), K. Yamaoka, Y.E. Nakagawa, S. Sugita (Aoyama Gakuin U.), M. Ohno, T. Takahashi, T. Asano, T. Uehara, Y. Fukazawa (Hiroshima U.), Y. Urata, M. Tashiro, K. Abe, K. Onda, Y. Sato, M. Suzuki (Saitama U.), T. Enoto, R. Miyawaki, K. Makishima (Univ. of Tokyo), M. Suzuki, T. Tamagawa, Y. Terada (RIKEN), K. Nakazawa, M. Kokubun, T. Takahashi (ISAS/JAXA), E. Sonoda, M. Yamauchi (Univ. of Miyazaki), on behalf of the Suzaku WAM team report: The bright, long GRB 070328 (Markwardt et al., GCN 6224; Stamatikos et al., GCN 6225) triggered the Suzaku Wide-band All-sky Monitor (WAM), which covers the energy range of 50 keV - 5 MeV, at 03:53:46 UT(=T0). The light curve shows multiple separate pulses with the T90 duration of about 38 seconds. The fluence in 100 keV - 3 MeV was 4.42 (-1.65, +0.54) x 10^-5 erg/cm^2, while the 1-s peak flux measured from T0+8 was 4.28 (-2.95, +0.18) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0+1 to T0+39 is described with a Band model as follows: the low-energy photon index alpha : -1.00 (-0.18, 0.21), the high-energy photon index beta : -1.89 (-0.43, 0.20), the Break energy E0 : 959 (-343, 664) keV, and the peak energy Epeak : 959 (-453, 1005) keV (chi^2/dof = 33.2/22). Fitting by a power law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) alpha 1.17 (-0.15 +0.14), and Epeak 1126 (-426, +868) keV (chi^2/dof = 37.6/23). All the quoted errors are at statistical 90% confidence level, while systematic errors are not included. The WAM light curve of this event is available at http://www.astro.isas.ac.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html