GRB 090829A, GRB 090829

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
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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

Colleen A. Wilson-Hodge reports on behalf of the Fermi GBM Team:

"At 16:07:38.86 UT on 29 August 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090829 (trigger 273254860 / 090829672).

The on-ground calculated location, using the GBM trigger data, is
RA = 329.2, DEC = -34.2 (J2000 degrees, equivalent to 21 h 57 m, 34 d 11'),
with an uncertainty of 1 degree (radius, 1-sigma containment, statistical
only; there is additionally a systematic error which is currently
estimated to be 2 to 3 degrees).
 
The angle from the Fermi LAT boresight is 47 degrees.
This burst triggered an automatic repoint of Fermi.

The GBM light curve, with a duration (T90) of about 85 s (8-1000 keV),
consists of a weak precursor followed by a bright peak. The
time-averaged spectrum from T0-6.1 s to T0+92 s is adequately fit by
a Band function with Epeak = 183 +/- 31 keV, alpha = -1.44 +/- 0.04,
and beta = -2.1 +/- 0.1

The event fluence (8-1000 keV) in this time interval is
(1.02 +/- 0.02)E-4 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+46 s in the 8-1000 keV band is 51.5 +/- 0.9 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."