[vsnet-grb-info 12507] GRB 121011B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13874
SUBJECT: GRB 121011B: Suzaku WAM observation of the prompt emission
DATE:    12/10/16 09:02:56 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno at hep01.hepl.hiroshima-u.ac.jp>

K. Takaki, Y. Hanabata,  T. Kawano, Y.Tanaka, R. Nakamura, M. Ohno,
Y. Fukazawa (Hiroshima U.),
A. Sakamoto, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara,
M. Asahina, S. Kobayashi, H. Ueno (Saitama U.),
M. Akiyama, N. Ohmori, E. Mochinaga, M. Yamauchi (Univ. of Miyazaki),
Y. E. Nakagawa (Waseda U.), S. Sugita (Nagoya U.), K. Yamaoka,
M. Kokubun, T. Takahashi (ISAS/JAXA), Y. Urata, P. Tsai (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report:

The short, IPN localized GRB 121011B (Golenetskii et al., GCN 13863)

triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 22:32:22.753 UT (=T0).
The observed light curve shows  a single peak structure starting at
T0 s, ending at T0+0.5 s,  with a duration (T90) of about 0.28 seconds.
The fluence in 100 - 1000 keV was 1.21 (-0.07, +0.15) x 10^-6 erg/cm^2
The 1-s peak flux measured from T0-0.5s  was 2.10 (-0.26, +0.15)
photons/cm^2/s in the same  energy range.

Preliminary result shows that the time-averaged spectrum from T0 to
T0+0.5s is well fitted by a power-law with exponential cutoff model:
   dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
   alpha       0.45 (-0.59, +0.50), and
   Epeak       810 (-139, 229) keV (chi^2/d.o.f. = 31.1/24).

We also shows the results with the same spectrum fitted by a GRB Band
model,
the low-energy photon index alpha: -0.39 (-0.53, +0.68),
the high-energy photon index beta: <-2.33
and the peak energy Epeak: 778 (-163, +237) keV
(chi^2/d.o.f = 30.3/23).

All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
The light curves for this burst are available at:

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