[AAVSO-HEN] GRB 091003A: Suzaku WAM observation of the prompt emission

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  9998
SUBJECT: GRB 091003A: Suzaku WAM observation of the prompt emission
DATE:    09/10/07 02:43:10 GMT
FROM:    Kenta Kono at Miyazaki U  <kenta0514 at astro.miyazaki-u.ac.jp>

K. Kono, E. Sonoda, N. Ohmori, K. Noda, 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 091003A
(Fermi-GBM trigger 276237347 / 091003191 ; A. Rau et al., GCN 9983 ; J.
McEnery et al., GCN 9985)
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 04:35:45.586 UT (=T0).

The observed light curve shows a multi-peaked structure
starting at T0-2 s and ending at T0+23 s, with a total duration (T90) of
about 21 s.

The fluence in 100 - 1000 keV was 1.98(-0.14, +0.08)x10-5 erg/cm2.
The 1-s peak flux measured from T0+18 s was 7.53(-1.28, +0.39)
photons/cm2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-2 s to T0+23 s is well fitted by a power-law with exponential cutoff
model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha 1.19(-0.36, +0.29), and
Epeak 576(-72, +106) keV (chi2/d.o.f. = 21.5/24).

Due to the brightness of this burst, a 3% systematic error
was added for low energy channels.
All the quoted errors are at 90% confidence level,

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