GCN Circular 9653

M. Ohno (ISAS/JAXA), W. Iwakiri (Saitama U.),
M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
M. Tashiro, Y. Terada, A. Endo, K. Onda, T. Sugasahara (Saitama U.),
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, E. Sonoda,
K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki),
K. Yamaoka, S. Sugita (Aoyama Gakuin U.), S. Hong (Nihon U.),
N. Vasquez (Tokyo Tech.), Y. Urata (NCU),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
on behalf of the Suzaku WAM team, report:


The bright, long GRB 090709A (Swift/BAT trigger #356890 ; Morris et
al., GCN 9625
Not found
 
 
) triggered the Suzaku Wide-band  All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at 07:38:33 UT (=T0).

The observed light curve shows a multi-peaked structure with a duration
(T90) of about 81 seconds. The corresponding peaks in the FFT power
spectrum of 1 s light curve are clearly seen around P=8.06(-0.20,+0.20) s,
which is consistent with the previous reports (Markwardt et al., GCN 9645
Not found
 
 
;
Golenetskii et al., GCN 9647
Not found
 
 
; Gotz et al., GCN 9649
Not found
 
 
).
The fluence in 100 - 1000 keV was 6.06(-0.36, +0.48) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+70s was 4.83(-0.69, +0.27) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-10s to T0+110s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       0.97(-0.43, +0.52), and
  Epeak       439(-58, -48) keV (chi^2/d.o.f. = 62.9/48).

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