GRB 070917: Suzaku WAM observation of the prompt emission
A. Endo, M. Tashiro, Y. Urata, K. Onda, M. Suzuki, N. Kodaka,
K. Morigami (Saitama U.), Y. Terada, T. Tamagawa (RIKEN),
M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira (Hiroshima U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo),
E. Sonoda, M.Yamauchi, S. Maeno, H. Tanaka, R. Hara (Univ. of
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), S. Hong (Nihon U.),
on behalf of the Suzaku WAM team, report:
The long GRB 070917 (Swift/BAT trigger #291292 ; Cummings et al.,
GCN 6791) triggered the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV
at 2007-09-17 07:33:56.500 UT (=T0).
The observed light curve shows a single peak starting at T0+0s, ending
at T0+3s with a duration (T90) of about 2.5 seconds. The fluence in
100 - 1000 keV was 2.4 (+0.2, -0.2) * 10^(-6) erg/cm2. The 1-s peak flux
measured from T0+0s was 3.1 (+0.3, -0.3) photons/cm2/s in the
same energy range.
Preliminary result shows that the time-averaged spectrum from T0+0s to
T0+3s is well fitted by a single power-law with a photon index
of 1.6 (+0.2, -0.2) (chi2/d.o.f. = 9.6/11).
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: