[vsnet-grb-info 13263] GRB 130504B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14600
SUBJECT: GRB 130504B: Suzaku WAM observation of the prompt emission
DATE:    13/05/08 04:30:55 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

T. Yasuda, M. Tashiro, Y. Terada, Y. Ishida, H. Ueno, S. Sugimoto
(Saitama U.), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui,
Y. Fukazawa (Hiroshima U.), M. Yamauchi, N. Ohmori, M. Akiyama
(Univ. of Miyazaki), 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 bright, short, IPN localized GRB 130504B (GCN 14560;  von Kienlin et
al., GCN 14561; Golenetskii et al.) triggered the Suzaku Wide-band
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV
at 07:32:03.063 UT (=T0).

The observed light curve shows a double-peaked structure starting at
T0+0.25 s, ending at T0+0.75 s with a duration (T90) of about
0.38 seconds.
The fluence in 100 - 1000 keV was 4.97(+0.15/-0.30) x10^-6 erg/cm^2.
The 1-s peak flux measured was 7.60 (+0.28/-0.54) 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       0.41 (+0.20/-0.22), and
Epeak      1321 (+139/-129) keV (chi^2/d.o.f. = 35.1/24).

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