TITLE: GCN CIRCULAR NUMBER: 10950 SUBJECT: GRB 100707A: Suzaku WAM observation of the prompt emission DATE: 10/07/10 07:02:25 GMT FROM: Yoshitaka Hanabata at Hiroshima U Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.) K. Yamaoka (Aoyama Gakuin U.), S. Sugita (Nagoya U.), Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, T. Yasuda (Saitama U.), M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata, H. M. Lin (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report: The long GRB 100707A (Fermi/GBM trigger #300156400; C. Wilson-Hodge et al., GCN 10944; Fermi-LAT detection; V. Pelassa et al., GCN 10945) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy of 50 keV - 5 MeV at 2010-07-07 00:46:38.91 UT (T=0). The observed light curve shows a FRED-like peak structure lasting from T0-0.5s to T0+18.5s with T90 of about 12 seconds. The fluence in 100 - 1000 keV was 5.26 (+/-0.27) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0+1.5s was 32.24 (-1.28, +1.22) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-0.5s to T0+18.5s is well fitted by a single power-law with a photon index of 2.15 (-0.05, +0.06) (chi^2/d.o.f = 39.4/25). Due to the brightness of this burst, a 3% systematic error was added for low energy channels. In addition, there might be some calibration uncertainties in these spectral parameters because GRB photons came to the WAM detector by passing through the large Ne dewar of the X-ray micro-calorimeter (XRS). All the errors are quoted at 90% confidence level. The light curves for this burst wiil be available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html