[vsnet-grb-info 7940] GRB 090528: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9483
SUBJECT: GRB 090528: Suzaku WAM observation of the prompt emission
DATE:    09/06/03 01:55:34 GMT
FROM:    Yujin E. Nakagawa at RIKEN  <yujin at crab.riken.jp>

Y. E. Nakagawa, T. Tamagawa (RIKEN), K. Yamaoka, S. Sugita (Aoyama Gakuin U.),
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),
S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), on behalf of the Suzaku WAM team,
report:

The long GRB 090528 (Fermi/GBM trigger 265176543 / 090528173, von Kienlin et al.,
GCN 9446) was detected by the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 04:09:01.00 UT (=T0). The observed
light curve shows a single-peaked structure lasting from T0-8s, ending at T0+28s,
with a duration (T90) of about 26.0 seconds. 

The fluence in 100 - 1000 keV was 1.9 (+0.2/-0.7) * 10^-6 erg/cm^2.
The 1-s peak flux measured from T0+2.5s was 0.5 (+0.2/-0.3) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-4s to T0+22s
is well fitted by a single power-law with a photon index of 2.6 (+0.7/-0.5)
(chi^2/d.o.f = 13/13). 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.ac.jp/suzaku/research/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html