[vsnet-grb-info 7760] GRB 090428B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9314
SUBJECT: GRB 090428B: Suzaku WAM observation of the prompt emission
DATE:    09/05/01 05:22:26 GMT
FROM:    Takeshi Uehara at Hiroshima U  <uehara at hirax7.hepl.hiroshima-u.ac.jp>

T. Uehara, Y. Hanabata, T. Takahashi, Y. Fukazawa(Hiroshima U.),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
K. Kono, E. Sonoda, M. Yamauchi, N. Ohmori, H. Hayashi,
K. Noda, A. Daikyuji, Y. Nishioka (Univ. of Miyazaki),
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 090428B (Fermi/GBM
trigger 262617313 / 090428552, Bissaldi et al., GCN 9295)
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 13:15:12.66 UT (=T0).
The observed light curve shows a single FRED-like peak
starting at T0-10s, ending at T0+9s, with a duration (T90) of about 19.0 seconds. 

The fluence in 100 - 1000 keV was 2.6(+0.5/-0.9) X10^-6 erg/cm^2.
The 1-s peak flux measured from T0+1s was 1.1 photons/cm^2/s in the same
energy range.

Preliminary result shows that the time-averaged spectrum from T0-10s to
T0+9s is well fitted by a single power-law with a photon index
of 2.0 (+0.5/-0.4) (chi^2/d.o.f = 5/7).
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