TITLE: GCN CIRCULAR NUMBER: 15453 SUBJECT: GRB 131024B: Suzaku WAM observation of the prompt emission DATE: 13/11/05 11:35:06 GMT FROM: Makoto Tashiro at Saitama U/Swift Y. Ishida, M. Tashiro, Y. Terada, T. Yasuda, H. Ueno, S. Sugimoto (Saitama U.), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui, Y. Fukazawa (Hiroshima U.), M. Yamauchi, N. Ohmori, M. Akiyama (Univ. of Miyazaki), K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.), Y. E. Nakagawa, M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri (RIKEN), Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report: The long GRB 131024B (Krimm et al. GCN 15371) was detected by the the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 21:35:31 UT (=T0). The observed light curve shows a single peak with a duration (T90) of about 45 seconds. The fluence in 100 - 1000 keV was 4.26 (+0.84/-2.27) x 10^-6 erg/cm^2. The 1-s peak flux measured from T0+2 s was 0.73 (+0.26/-0.55) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-5 s to T0+5 s is well fitted by a single power-law with a photon index of 2.13 (+0.28/-0.36) (chi^2/d.o.f = 12.4/14). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst will be available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html