[vsnet-grb-info 7592] GRB 090411B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9147
SUBJECT: GRB 090411B: Suzaku WAM observation of the prompt emission
DATE:    09/04/18 10:04:13 GMT
FROM:    Masanori Ohno at ISAS/JAXA  <ohno at astro.isas.jaxa.jp>

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),
T. Uehara, T. Takahashi, Y. Fukazawa, Y. Hanabata (Hiroshima U.),
E. Sonoda, M. Yamauchi, 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 long GRB 090411B (Fermi-GBM trigger #261186466/090411991;
 Preece et al., GCN 9131)
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
 energy range of 50 keV - 5 MeV at 23:47:38 UT (=T0).
The observed light curve shows a multi-peaked structure starting at T0-1s,
ending at T0+25s with a duration (T90) of about 20 seconds.
The fluence in 100 - 1000 keV was 7.6 +/- 0.3 x 10^-6 erg/cm^2.
The 1-s peak flux measured from T0+6s was 2.3 +/- 0.2 photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-1s to
T0+22s is well fitted by a single power-law with a photon index
of 2.4 +/- 0.1 (chi^2/d.o.f = 23.2/21).

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