[vsnet-grb-info 4468] GRB 070328: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6240
SUBJECT: GRB 070328: Suzaku WAM observation of the prompt emission
DATE:    07/04/03 12:56:49 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

S. Hong (Nihon U.), 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 (Saitama U.), 
T. Enoto, R. Miyawaki, K. Makishima (Univ. of Tokyo), 
M. Suzuki, T. Tamagawa, Y. Terada (RIKEN), 
K. Nakazawa, M. Kokubun, T. Takahashi (ISAS/JAXA), 
E. Sonoda, M. Yamauchi (Univ. of Miyazaki), 
on behalf of the Suzaku WAM team report:

The bright, long GRB 070328 (Markwardt et al., GCN 6224;
Stamatikos et al., GCN 6225) triggered the Suzaku Wide-band All-sky
Monitor (WAM), which covers the energy range of 50 keV - 5 MeV, at
03:53:46 UT(=T0).  The light curve shows multiple separate pulses with
the T90 duration of about 38 seconds. The fluence in 100 keV - 3 MeV
was 4.42 (-1.65, +0.54) x 10^-5 erg/cm^2, while the 1-s peak flux
measured from T0+8 was 4.28 (-2.95, +0.18) photons/cm^2/s in the same
energy range.

Preliminary result shows that the time-averaged spectrum from T0+1 to 
 T0+39 is described with a Band model as follows:

 the low-energy photon index alpha : -1.00 (-0.18, 0.21),
 the high-energy photon index beta : -1.89 (-0.43, 0.20),
 the Break energy E0 :       959 (-343, 664) keV,
 and the peak energy Epeak : 959 (-453, 1005) keV (chi^2/dof = 33.2/22).

Fitting by a power law with exponential cutoff model:

  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak)
  alpha       1.17 (-0.15 +0.14), and
  Epeak       1126 (-426, +868) keV (chi^2/dof = 37.6/23).

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

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