[vsnet-grb-info 8750] GRB 091123: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10250
SUBJECT: GRB 091123: Suzaku WAM observation of the prompt emission
DATE:    09/12/07 01:56:40 GMT
FROM:    Norisuke Ohmori at Miyazaki U  <ohmori at astro.miyazaki-u.ac.jp>

N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, Y.Nishioka,
K. Noda, M. Yamauchi (Univ. of Miyazaki), M. Ohno, M. Suzuki, 
M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka (Aoyama  Gakuin U.),
S. Sugita (Nagoya U.), T. Sugasahara, M. Tashiro, Y. Terada, A. Endo, 
K. Onda, W. Iwakiri (Saitama U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), 
N. Vasquez (Tokyo Tech.), Y. Urata, H.M  Lin (NCU), Y. Hanabata, 
T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), T. Enoto, 
K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.), 
on behalf of the Suzaku WAM team, report

The very long GRB 091123 (Fermi-GBM trigger #280652919 / 091123298; 
McBreen et al., GCN 10226) was detected by the the Suzaku Wide-band 
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV 
at 07:07:42 UT (=T0).

The observed light curve shows several pulses with a total duration of 
at least 650 s. The first bright emission episode was seen starting at 
T0-90 s, ending at T0+90 s. After the emission returned to the background 
level, three pulses was observed again at T0+220 s, T0+450 s, and T0+600 s, 
respectively.

The fluence in 100 - 1000 keV was 3.78 (-0.59, +0.45) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+45s was 2.08 (-0.31, +0.27) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-90s to
T0+607s is fitted by a single power-law with a photon index
of 2.30 (-0.14, +0.16) (chi^2/d.o.f. = 63.4/99).

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