TITLE: GCN CIRCULAR NUMBER: 9061 SUBJECT: GRB 090324: Suzaku WAM observation of the prompt emission DATE: 09/03/31 17:50:35 GMT FROM: Kazutaka Yamaoka at Aoyama Gakuin U M. Suzuki, M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA), N. Kodaka, W. Iwakiri, M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda, K. Morigami, T. Sugasahara (Saitama U.), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita, K. Yamaoka (Aoyama Gakuin U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata (Hiroshima U.), E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono, H. Hayashi (Univ. of Miyazaki), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), on behalf of the Suzaku WAM team, report: The long GRB 090324 localized by SuperAGILE (Feroci et al., GCN 9029) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 02:47:17.604 UT (=T0). The observed light curve shows a double-peaked structure starting at T0-1s, with a duration (T90) of about 70 seconds. We note that the second peak starting around T0+50s corresponds to the FRED-like pulse observed by SuperAGILE. The fluence in 100 - 1000 keV was 8.8(-2.4, +1.0)x10^-6 erg/cm^2. The 1-s peak flux measured from T0+59s was 0.99(-0.12, +0.05) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-1s to T0+89s is well fitted by a single power-law with a photon index of 2.0(-0.2, +0.3) (chi^2/d.o.f = 10.1/13). From a time resolved analysis of the first peak (T0-1s to T0+49s) and the second peak (T0+49s to T0+89s), we found that both spectra were fitted by single power-law models. There is hard to soft spectral evolution from the first peak to the second peak; corresponding photon indices of the first and the second intervals are 1.7+/-0.3 and 2.4(-0.3, +0.4) respectively. 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