[vsnet-grb-info 8373] GRB 090829A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9896
SUBJECT: GRB 090829A: Suzaku WAM observation of the prompt emission
DATE:    09/09/05 03:02:48 GMT
FROM:    Kazuhiro Noda at Miyazaki U  <kaz1206 at astro.miyazaki-u.ac.jp>

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

The long GRB 090829A (Fermi-GBM trigger #273254860 / 090829672 ;
Colleen et al., GCN9849)
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 2009-08-29 16:08:14.99 UT (=T0).

The observed light curve shows a multi-peaked structure, starting at
T0-40 s and ending at T0+60 s, with a total duration (T90) of about 30 s.
The fluence in 100 - 1000 keV was 5.65(-1.19, +0.34) x10-5 erg/cm2.
The 1-s peak flux measured from T0+12 s was 13.07(-1.00, +0.81)
photons/cm2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-40 s to T0+60s is well fitted by a power-law with exponential cutoff
model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha: 1.52(-0.29, +0.26), and
Epeak: 344(-52, +91) keV (chi2/d.o.f. = 50.7/36).

All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html