[vsnet-grb-info 7265] GRB 090117C: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8836
SUBJECT: GRB 090117C: Suzaku WAM observation of the prompt emission
DATE:    09/01/22 12:37:45 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

M. Suzuki, M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA),
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.),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira (Hiroshima U.), 
S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), on behalf of
the Suzaku WAM team, report:

The long GRB 090117C (Connaughton et al., GCN8822) triggered the
Suzaku Wide-band All-sky Monitor (WAM) which covers an energy
range of 50 keV - 5 MeV at 2009-01-17 15:10:40 UT (=T0).

The observed light curve shows relatively strong emission from
T0-6 s to T0+32 s with a precursor of about 1 min. long.
The duration (T90) including the precursor is about 91 seconds.
The fluence in 100 - 1000 keV was (1.18 +/- 0.11) x 10^-5 erg/cm^2.
The 1-s peak flux measured from T0+22 s was 1.2 (+/-0.3)
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-78 s
to T0+32 s is fitted by a single power-law with a photon index
of 1.72 +/- 0.18 (chi^2/d.o.f = 14/12).

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.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html