TITLE: GCN CIRCULAR NUMBER: 10168 SUBJECT: GRB 091109B: Suzaku WAM observation of the prompt emission DATE: 09/11/14 09:30:39 GMT FROM: Masanori Ohno at ISAS/JAXA M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka (Aoyama Gakuin U.), S. Sugita (Nagoya U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, Y. Nishioka, K. Noda, M. Yamauchi (Univ. of Miyazaki), Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), W. Iwakiri, M. Tashiro, Y. Terada, A. Endo, K. Onda, T. Sugasahara (Saitama U.), Y. Urata, H.M Lin (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report: The short GRB 091109B (Swift/BAT trigger #375409 ; Oates et al., GCN 10148) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 2009-11-09 21:49:02.83 UT (=T0). The observed light curve shows a single peak starting at T0+0.3s, ending at T0+0.6s with a duration (T90) of about 0.19 seconds. The fluence in 100 - 1000 keV was 9.98(-3.69,+0.72) x 10^-7 erg/cm^2. The 1-s peak flux measured from T0 was 1.75(-0.59,+0.14) photons/ cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0s to T0+1s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha 0.91(-0.78,+0.42), and Epeak 1330(-610,+1120) keV (chi^2/d.o.f. = 24.6/24). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html