[vsnet-grb-info 7221] GRB 090107B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8794
SUBJECT: GRB 090107B: Suzaku WAM observation of the prompt emission
DATE:    09/01/10 14:30:59 GMT
FROM:    Yujin E. Nakagawa at RIKEN  <yujin at crab.riken.jp>

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

The long GRB 090107B (Gotz et al., GCN 8786) was detected by the
Suzaku Wide-band  All-sky Monitor (WAM) which covers an energy range
of 50 keV - 5 MeV at 2009-01-07 16:20:35 UT (=T0).

The observed light curve shows a double-peaked structure lasting from
T0-1 s to T0+20 s with a duration (T90) of about 14 seconds. The fluence
in 100 - 1000 keV was 1.3 (+0.7, -0.9) * 10^-6 erg/cm^2. The 1-s peak
flux measured from T0+13 s was 0.4 +/- 0.3 photons/cm^2/s in the same 
energy range.

Preliminary result shows that the time-averaged spectrum from T0-1 s
to T0+20 s is well fitted by a single power-law with a photon index 
of 2.0 +/- 0.4 (chi^2/d.o.f = 6/10).

All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves with 1-sec time resolution for this burst will be appeared at:

 http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html