[vsnet-grb-info 13264] GRB 130504C: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14601
SUBJECT: GRB 130504C: Suzaku WAM observation of the prompt emission
DATE:    13/05/08 04:31:01 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, long GRB 130504C (GCN 14574; Fermi-LAT detection : Kocevski
et al.) triggered the Suzaku Wide-band  All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 23:29:00.540 UT (=T0).

The observed light curve shows a multi-peaked structure starting at T0-9
s, ending at T0+110 s with a duration (T90) of about 67 seconds.
The fluence in 100 - 1000 keV was 9.11 (+0.14/-0.51) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+ 27 s was
15.9 (+0.3/-4.0) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-9 s to T0+110 s is well fitted by a GRB Band model as follows.
the low-energy photon index alpha:  -1.59 (+0.17/-0.12),
the high-energy photon index beta: -2.43 (+0.17/-0.33),
and the peak energy Epeak: 845 (+227/-159) keV (chi^2/d.o.f = 77.0/50).

Due to the brightness of this burst, a 1% systematic error was added for
low energy channels.
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