[vsnet-grb-info 7526] GRB 090401B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9084
SUBJECT: GRB 090401B: Suzaku WAM observation of the prompt emission
DATE:    09/04/04 07:04:06 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

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

The bright long GRB 090401B (Swift/BAT trigger #348152; Schady et al. 
GCN 9066; Stamatikos et al., GCN 9068) triggered the Suzaku Wide-band 
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV 
at 08:35:24.504 UT (=T0).

The observed light curve shows a multi-peaked structure
lasting from T0+0s to T0+10s with a duration (T90) of about 9 seconds. 
The fluence in 100 - 1000 keV was 2.56 (-0.11,+0.09) x 10^-5 erg/cm^2. 
The 1-s peak flux measured from T0+7s was 21.6 (-1.5,+1.3) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0+0s to
T0+10s is well fitted by a single power-law with a photon index
of 2.22 (-0.09,+0.10) (chi^2/d.o.f = 24.9/25).

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