[vsnet-grb-info 12640] GRB 121118B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14000
SUBJECT: GRB 121118B: Suzaku WAM observation of the prompt emission
DATE:    12/11/26 03:04:30 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno at hep01.hepl.hiroshima-u.ac.jp>

T. Kawano, M. Ohno, Y. Hanabata, Y. Tanaka, R. Nakamura, K Takaki,
Y. Fukazawa (Hiroshima U.),
A. Sakamoto, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara,
M. Asahina, S. Kobayashi, H. Ueno (Saitama U.),
M. Akiyama, N. Ohmori, E. Mochinaga, M. Yamauchi (Univ. of Miyazaki),
Y. E. Nakagawa (Waseda U.), S. Sugita (Nagoya U.), K. Yamaoka,
M. Kokubun, T. Takahashi (ISAS/JAXA), Y. Urata, P. Tsai (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report:


The long, IPN localized GRB 121118B: (Hurley et al., GCN 13977)
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 22:27:6.662 UT (=T0).

The observed light curve shows a multi-peaked structure starting at
T0-30 s, ending at T0+70 s, with a duration (T90) of about 50
seconds. The fluence in 100 - 1000 keV was 4.52(-1.27 +0.85) x 10^-5
erg/cm^2. The 1-s peak flux measured from T0-0.5s was 8.48(-0.64 +0.56)
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-30s to
T0+70s is well fitted by a power-law with exponential cutoff model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha 1.39(-0.67 +0.50), and
Epeak 450(-224 +121) keV (chi^2/d.o.f. = 28.5/22).

All the quoted errors are at statistical 90% confidence level.
Due to the brightness of this burst, a 3% systematic error was added
for low energy channels.

The light curves for this burst will be available at:

http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html