[vsnet-grb-info 3857] GRB 060928: Suzaku/WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5688
SUBJECT: GRB 060928: Suzaku/WAM observation of the prompt emission
DATE:    06/10/04 16:59:22 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno at hirax7.hepl.hiroshima-u.ac.jp>

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

  The bright, long burst, GRB 060928 (Hurley et al., GCN 5684), 
  triggered the Suzaku Wideband All-sky Monitor (WAM), which covers 
  the energy range of 50 keV - 5 MeV, at 01:17:01.74 (UT).
  Two distinct strong bursts were seen in the light curve observed
  with the WAM. The duration of the first and second burst was 
  about 14 seconds and 70 seconds, respectively. These two bursts 
  were separated by about 200 seconds. 
  Here we report the analysis result only for the first burst.
  The fluence in 100 - 1000 keV was 2.18(-0.11, +0.11)x10-5 erg/cm2,
  while the 1-s peak flux was 9.75(-0.47, +0.51) photons/cm2/s in the
  same energy range.

  Preliminary result shows that the time-averaged spectrum is
  well described by a power law with an exponential
  cutoff as follows.

  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak)
  alpha       1.18 (-0.18, +0.17), and
  Epeak       580  (-70,   +112) keV.
  
  All the quoted errors are at statistical 90% confidence level,
  while systematic errors are not included.


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