[vsnet-grb-info 4474] GRB 070402: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6246
SUBJECT: GRB 070402: Suzaku WAM observation of the prompt emission
DATE:    07/04/06 07:31:58 GMT
FROM:    Eri Sonoda at U of Miyazaki/Japan  <sonoda at astro.miyazaki-u.ac.jp>

E. Sonoda, M. Yamauchi (Univ. of Miyazaki),
K. Yamaoka, Y.E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
M. Ohno, T. Takahashi, T. Asano, T. Uehara, Y. Fukazawa (Hiroshima U.),
Y. Urata, M. Tashiro, K. Abe, K. Onda, Y. Sato, M. Suzuki, N. Kodaka (Saitama U.),
T. Enoto, R. Miyawaki, K. Makishima (Univ. of Tokyo),
M. Suzuki, T. Tamagawa, Y. Terada (RIKEN), S. Hong (Nihon U.),
K. Nakazawa, M. Kokubun, T. Takahashi (ISAS/JAXA),
on behalf of the Suzaku WAM team report:

The IPN-localized long GRB 070402 (Hurley et al., GCN 6241 and 6242)
triggered the Suzaku Wide-band All-sky Monitor (WAM), which covers the
energy range of 50 keV - 5 MeV, at 15:48:35 UT (=T0).
The light curve shows multiple separate pulses with the total
duration of about 17 s. The fluence in 100 keV - 3 MeV was
1.09 (-0.15, +0.06) x 10 ^-5 erg/cm2, while the 1-s peak flux measured
from T0+5 s was 5.55 (-0.43, +0.30) photons/cm2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0 to T0+12 s
can be described by a power law with an exponential cutoff model as follows:

dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha = 1.29 (-0.23, +0.21) and
Epeak = 376 (-46, +74) keV (chi2/d.o.f. = 67/48).

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