[vsnet-grb-info 12441] GRB 120916A Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13816
SUBJECT: GRB 120916A Suzaku WAM observation of the prompt emission
DATE:    12/09/25 05:23:37 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

H. Ueno, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, M. Asahina,
S. Kobayashi, A. Sakamoto, Y. Ishida, S. Sugimoto (Saitama U.),
M. Akiyama, N. Ohmori, M. Yamauchi (Univ. of Miyazaki),
K. Yamaoka, Y. E. Nakagawa (Waseda U.),
Y. Hanabata, T. Kawano, K. Takaki, R. Nakamura, Y.Tanaka, M. Ohno,
Y. Fukazawa (Hiroshima U.), S. Sugita (Nagoya U.),
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 long GRB 120916A (Fermi-LAT detection: Vianello et al., GCN 13777;
IPN detection and localization: Hurley et al., GCN 13778) triggered
the Suzaku Wide-band  All-sky Monitor (WAM) which covers an energy range
of 50 keV - 5 MeV at 04:07:46.689 UT (=T0).

The observed light curve shows a multi-peaked main structure starting
at T0-2 s, ending at T0+30 s with the total duration (T90) is about 26
seconds.
A weaker and softer pulse followed the main component from T0+50 s to
T0+60 s.
The fluence of main pulse in 100 - 1000 keV was
1.11 (-0.09, +0.13) x 10^-5 erg/cm^2

The 1-s peak flux measured at T0+23 s was
5.25 (-0.41, +0.46) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-2 s
to T0+28 s is well fitted by a power-law with exponential cutoff model:

dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha : 0.97(-1.01, +0.70)
  Epeak : 342 (-72, +106) keV (chi^2/d.o.f = 5.18/14).

Due to the brightness of this burst, a 3% systematic error was added
for low energy channels. All the quoted errors are at statistical 90%
confidence level.

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html