TITLE: GCN CIRCULAR NUMBER: 14000 SUBJECT: GRB 121118B: Suzaku WAM observation of the prompt emission DATE: 12/11/26 03:04:30 GMT FROM: Masanori Ohno at Hiroshima U T. Kawano, M. Ohno, Y. Hanabata, Y. Tanaka, R. Nakamura, K Takaki, Y. Fukazawa (Hiroshima U.), A. Sakamoto, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara, M. Asahina, S. Kobayashi, H. Ueno (Saitama U.), M. Akiyama, N. Ohmori, E. Mochinaga, M. Yamauchi (Univ. of Miyazaki), Y. E. Nakagawa (Waseda U.), S. Sugita (Nagoya U.), K. Yamaoka, M. Kokubun, T. Takahashi (ISAS/JAXA), Y. Urata, P. Tsai (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report: The long, IPN localized GRB 121118B: (Hurley et al., GCN 13977) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 22:27:6.662 UT (=T0). The observed light curve shows a multi-peaked structure starting at T0-30 s, ending at T0+70 s, with a duration (T90) of about 50 seconds. The fluence in 100 - 1000 keV was 4.52(-1.27 +0.85) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0-0.5s was 8.48(-0.64 +0.56) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-30s to T0+70s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha 1.39(-0.67 +0.50), and Epeak 450(-224 +121) keV (chi^2/d.o.f. = 28.5/22). All the quoted errors are at statistical 90% confidence level. Due to the brightness of this burst, a 3% systematic error was added for low energy channels. The light curves for this burst will be available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html