[vsnet-grb-info 8038] GRB 090623: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9577
SUBJECT: GRB 090623: Suzaku WAM observation of the prompt emission
DATE:    09/06/26 03:41:48 GMT
FROM:    Yujin E. Nakagawa at RIKEN  <yujin at crab.riken.jp>

Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, E. Sonoda,
K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka,
S. Sugita (Aoyama Gakuin U.), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
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),
on behalf of the Suzaku WAM team,
report:

The long GRB 090623 (Fermi/GBM trigger 267417259 / 090623107, Rau et al.,
GCN 9566) was detected by the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 02:34:17.04 UT (=T0). The observed
light curve shows a multi-peaked structure lasting from T0-2 s, ending at
T0+48 s, with a duration (T90) of about 38 seconds. 

The fluence in 100 - 1000 keV was 2.7 (-0.9, +0.2) * 10^-5 ergs/cm^2.
The 1-s peak flux measured from T0+0.5 s was 5.3 (-1.2, +0.3) photons/cm^2/s 
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-2 s to T0+48 s
is well fitted by a power-law with an exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha        1.0(-0.3, +0.3), and
  Epeak        601(-100, +147) keV (chi2^/d.o.f. = 15/18).
 
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
 
The light curves for this burst is available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html