[vsnet-grb-info 14297] GRB 131216A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15611
SUBJECT: GRB 131216A: Suzaku WAM observation of the prompt emission
DATE:    13/12/26 00:50:21 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

T. Nagayoshi, M. Tashiro, Y. Terada, S. Koyama, T. Yasuda, S. Takeda,
Y. Ishida, H. Ueno, S. Sugimoto (Saitama U.), M. Yamauchi, N. Ohmori, M. 
Akiyama, R. Kinoshita (Univ. of Miyazaki), M. Ohno, K. Takaki,
T. Kawano, R. Nakamura, S. Furui, Y. Fukazawa (Hiroshima U.),
K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.), Y. E. Nakagawa,
M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri(RIKEN),
Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report:

The GRB 131216A (Fermi LAT detection: Veres et al.,GCN Circ. 15598,
IPN localization:Hurley et al., GCN Circ. 15600) triggered the Suzaku
Wide-band All-sky Monitor (WAM) which covers an energy range of
50 keV - 5 MeV at 01:56:32.11 UT (=T0).

The observed light curve shows a single FRED-like peak starting at
T0-1 s, ending at T0+8s, with a duration T90 of 5.69 seconds.
The fluence in 100 - 1000 keV was 7.46 (+0.99/-0.86) x10^-6 erg/cm^2.
The 1-s peak flux measured from T0+2s was
6.05 (+0.50/-0.73) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum fromT0-1s
to T0+8s is well fitted by a power-law with exponential cutoff model:

    dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
    alpha 1.42(+0.05/-0.73), and
    Epeak 400(+135/-142) keV (chi^2/d.o.f. = 15.5/13).

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