[vsnet-grb-info 14354] GRB 131229A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15668
SUBJECT: GRB 131229A: Suzaku WAM observation of the prompt emission
DATE:    14/01/03 16:01:44 GMT
FROM:    Tetsuya Yasuda at Saitama U  <yasuda at heal.phy.saitama-u.ac.jp>

T. Yasuda, M. Tashiro, Y. Terada, S. Koyama, S. Takeda, Y. Ishida,
H. Ueno, S. Sugimoto, T. Nagayoshi (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 long GRB 131229A (Swift/BAT trigger #582374; M. J. Page et al., GCN 15627) triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 06:39:29.971 UT (=T0). 

The observed light curve shows a multi-peaked structure starting at T0-6 s, ending at T0+13 s with a duration (T90) of about 12 s. The fluence in 100 - 1000 keV was 2.35 (+0.28/-0.30) x10^-5 erg/cm^2. The 1-s peak flux measured from T0+9 s was 13.7 (+0.8/-0.8) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-6 s to T0+13 s is well fitted by a power-law with exponential cutoff model:
dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha       1.05 (+0.67/-0.80), and
Epeak       405 (+78/-156) keV (chi^2/d.o.f. = 8.2/10).

All the quoted errors are at statistical 90% confidence level.

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