TITLE: GCN CIRCULAR NUMBER: 15942 SUBJECT: GRB 140304A: Suzaku WAM observation of the prompt emission DATE: 14/03/10 07:14:31 GMT FROM: Kazutaka Yamaoka at Nagoya U W. Iwakiri (RIKEN), M. Tashiro, Y. Terada, T. Yasuda, Y. Ishida, H. Ueno, S. Sugimoto, S. Koyama, S. Takeda, T. Nagayoshi (Saitama U.), M. Yamauchi, N. Ohmori, M. Akiyama, R. Kinoshita (Univ. of Miyazaki), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui, Y. Fukazawa (Hiroshima U.), K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.), Y. E. Nakagawa, M. Kokubun, T. Takahashi (ISAS/JAXA), Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report: The long GRB 140304A (Swift/BAT trigger #590206 ; Evans et al., GCN 15915; Fermi-GBM detection: Jenke and Fitzpatrick, GCN 15923) was detected by the the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 13:22:33 UT (=T0). The observed light curve shows a multi-peaked structure lasting from T0-3 s to T0+11 s with a duration (T90) of about 12 seconds. The fluence in 100 - 1000 keV was 1.69 (+0.32/-0.34) x10^-6 erg/cm^2. The 1-s peak flux measured from T0-1 s was 0.48 (+0.28, -0.23) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-3 s to T0+11 s is well fitted by a single power-law with a photon index of 2.09 (+0.66/-0.38) (chi^2/d.o.f = 12.3/14). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves with 1-sec time resolution for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html