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GCN Circular 12607

GRB 111121A: Suzaku WAM observation of the prompt emission
2011-12-01T10:39:34Z (12 years ago)
Yuji Urata at Nat. Central U. <>
C-J. Chuang, Y. Urata, P. Tsai (NCU), Y. Hanabata, T. Uehara,
T. Takahashi, M. Mizuno, M. Ohno, Y. Fukazawa (Hiroshima U.),
T. Yasuda, Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, M. Asahina,
S. Kobayashi, A. Sakamoto (Saitama U.), S. Sugita (Nagoya U.),
K. Yamaoka (Aoyama Gakuin U.), M. Kokubun, T. Takahashi (ISAS/JAXA),
Y. E. Nakagawa (Waseda U.), N. Ohmori, M. Akiyama, M. Yamauchi
(Univ. of Miyazaki), K. Nakazawa, K. Makishima (Univ. of Tokyo),
on behalf of the Suzaku WAM team, report:

The bright short GRB 111121A (Swift/BAT trigger 508161 ; D'Elia et
al., GCN 12578) was detected by the the Suzaku Wide-band All-sky
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at
16:26:24.488 UT (=T0).

The observed light curve shows a single peak structure starting at T0,
ending at T0+1 s with a duration (T90) of about 0.45 seconds. The
fluence in 100 - 1000 keV was 4.29(-0.41, 0.23) x 10^-6 erg/cm^2. The
1-s peak flux measured from T0+1 s was 20.26 photons/cm^2/s in the
same energy range.

Preliminary result shows that the time-averaged spectrum from T0 to
T0+1 s is well fitted by a power-law with exponential cutoff model:

  dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha   0.58 (-0.19, 0.18), and
  Epeak   1678.97 (-210.66, 300.31) keV (chi^2/d.o.f. = 60.1/47).

The light curves for this burst are available at:
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