[vsnet-grb-info 7158] GRB 081224: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8739
SUBJECT: GRB 081224: Suzaku WAM observation of the prompt emission
DATE:    08/12/27 03:55:50 GMT
FROM:    Hidenori Hayasi at Miyazaki U  <hayasi at astro.miyazaki-u.ac.jp>

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

The long, bright GRB 081224 (Fermi-GBM trigger #251846276; Colleen et
al., GCN 8725) triggered the Suzaku Wide-band All-sky Monitor (WAM)
 which covers an energy range of 50 keV - 5 MeV at 2008-12-24 21:17:55.214 UT (=T0).

The observed light curve shows a FRED-like peak structure
starting at T0-0.2s, ending at T0+19.8s with a duration (T90) of about 10.3 seconds.
The fluence in 100 - 1000 keV was 2.87(+0.09, -0.04) erg/cm^2.
The 1-s peak flux measured from T0+2s - T0+3s was 16.95(+0.91, -0.55) photons/cm^2/s in the same
 energy range.

Preliminary result shows that the time-averaged spectrum from
T0-0.2s to T0+19.8s is well fitted by a power-law with exponential cutoff model
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       0.83(+0.27, -0.28), and
  Epeak       447(+57, -40) keV (chi^2/d.o.f. = 19/22).

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