[vsnet-grb-info 7365] GRB 090301A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8929
SUBJECT: GRB 090301A: Suzaku WAM observation of the prompt emission
DATE:    09/03/04 15:39:51 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo),
Y. Hanabata, Y. Fukazawa, T. Takahashi, T. Uehara, C. Kira (Hiroshima U.),
Y. Terada, M. Tashiro, Y. Urata, A. Endo, K. Onda, N. Kodaka,
K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.), M. Ohno,
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), K. Yamaoka,
S. Sugita (Aoyama Gakuin U.), Y.E. Nakagawa, T. Tamagawa (RIKEN),
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 090301A (Swift/BAT trigger #344582; Fenimore et al., GCN 8923) 
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers 
an energy range of 50 keV - 5 MeV at 06:55:50.862 UT (=T0).

The observed light curve shows a multi-peaked structure lasting from T0-2s 
to T0+48s with a duration (T90) of about 35 seconds. The fluence in 100 - 
1000 keV was 6.9(-0.5, +0.1) x 10^-5 erg/cm^2.  The 1-s peak flux measured 
from T0+27 was 14.8(+/-0.9) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from 
T0-2s to T0+48s is fitted by a GRB Band model as follows.
the low-energy photon index alpha: -0.93 (-0.16, +0.18),
the high-energy photon index beta: -2.82 (-0.74, +0.29),
the break energy E0:       536 (-101, +131) keV,
and the peak energy Epeak: 574 +/- 170 keV (chi^2/d.o.f = 68/56).

Due to the high counting rate of this GRB, a 1% systematic error 
 was added for low energy channels. 
All the quoted errors are at the 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