[vsnet-grb-info 6852] GRB 081024B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8444
SUBJECT: GRB 081024B: Suzaku WAM observation of the prompt emission
DATE:    08/10/29 09:50:05 GMT
FROM:    Yoshitaka Hanabata at Hiroshima U  <hanabata at hep01.hepl.hiroshima-u.ac.jp>

Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira (Hiroshima 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), 
M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda, 
N. Kodaka, K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.),
E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori (Univ. of Miyazaki),
S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:

The short/hard GRB081024B (Fermi-LAT detected ; Omodei GCN8407,
Fermi-GBM triggered ; Connaughton and Briggs, GCN 8408) triggered the
Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range
of 50 keV - 5 MeV at 21:22:40.526 UT (=T0). 

The observed light curve shows double-peaked structure with a duration
(T90) of about 0.4 second. 
The fluence in 100 - 1000 keV was 2.7(+0.7, -1.0) X 10^-7 erg/cm^2. 
The peak flux within 0.5 second was 1.1(+0.3, -0.5) photons/cm^2/s in
the same energy range.

Preliminary result shows that even at least 2 MeV photons have been
detected, and the time-averaged spectrum from T0 to T0+0.5s is well
fitted by a single power-law with a photon index of 1.24(+0.25, -0.19)
(chi^2/d.o.f = 12.3/14). 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 availabel at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html