[vsnet-grb-info 4888] GRB 070704: Suzaku/WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6616
SUBJECT: GRB 070704: Suzaku/WAM observation of the prompt emission
DATE:    07/07/10 11:39:17 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno at hirax7.hepl.hiroshima-u.ac.jp>

C. Kira, M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
K. Morigami, N. Kodaka, K. Onda, M. Tashiro, M. Suzuki,Y. Urata, A. Endo (Saitama U.),
T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo),
S. Hong (Nihon U.),
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA),
E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara(Univ. of Miyazaki),
T. Tamagawa, Y. Terada (RIKEN), 
and Suzaku WAM team report:

The long burst, GRB 070704 (Swift/BAT trigger #283791; T. Sakamoto et al., GCN Circ. 6594;
A. Melandri et al., GCN Circ. 6602; S. Karpov et al., GCN Circ.6603) was triggered 
at T0=2007-07-04 20:05:02 UT by Suzaku Wide-band All-sky Monitor (WAM)
which covers the energy range of 50 keV - 5 MeV.
The observed light curve shows the multiple peaked structures 
with a duration (T90 in the 50-5000 keV band) of nearly 35 seconds.
According to the GCN Report 69.2, the light curve observed by Swift BAT shows an upsurge
around T0+350, while in the light curve by Suzaku WAM, there is no such a structure.

The fluence in the 100-1000 keV band was (8.4+/-1.7)*10^-6 erg/cm^2,
and the 1-s peak flux in the same band was 0.19+/-0.06 photons/cm^2/s.
Preliminary result shows that the time-averaged spectrum from T0-5 to T0+40 is
well fitted by single power law with a photon index of 2.0+/-0.4 in 100-1000 keV range.

All the quoted errors are at the 90% confidence level, 
while systematic errors are not included.

The WAM light curve of this event is available at the following URL.
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html