TITLE: GCN CIRCULAR NUMBER: 12347 SUBJECT: GRB 110903A: Suzaku WAM observation of the prompt emission DATE: 11/09/16 11:59:17 GMT FROM: Yoshitaka Hanabata at Hiroshima U Y. Hanabata, T. Uehara, T. Takahashi, M. Mizuno, M. Ohno, Y. Fukazawa (Hiroshima U.), T. Yasuda, Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, M. Asahina, S. Kobayashi, A. Sakamoto (Saitama U.), S. Sugita (Nagoya U.), K. Yamaoka (Aoyama Gakuin U.), M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa (Waseda U.), N. Ohmori, M. Akiyama, M. Yamauchi (Univ. of Miyazaki), Y. Urata, P. Tsai, C-J. Chuang (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report: The very long, bright GRB110903A (Mereghetti et al. GCN 12322) was detected by the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 02:39:34.298 UT (=T0). The observed light curve shows a multi-peaked structure starting at T0-57 s, ending at T0+364 s with a duration (T90) of about 340 secnds. There is a possible precursor at T0-57 s with a duration of about 15 seconds. The fluence in 100 - 1000 keV was 2.18 (-0.47, +0.22) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0+198 s was 2.45 (-0.20, +0.17) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0 to T0+364 s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha : 1.19 (-0.44, +0.54), and Epeak : 281 (-78, +33) keV (chi^2/d.o.f. = 39.2/31). All the quoted errors are at statistical 90% confidence level. The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html