[vsnet-grb-info 13262] GRB 130505A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14599
SUBJECT: GRB 130505A: Suzaku WAM observation of the prompt emission
DATE:    13/05/08 04:30:49 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 13505A (GCN 14563; Cannizzo et al.)
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at  UT 08:22:24.527 (=T0).

The observed light curve shows a bright peak followed by a weaker
emission seen up to T0+30 s with a duration (T90) of about 14 seconds.
The fluence in 100 - 1000 keV was 1.06 (+0.05/-0.05) x10^-4 erg/cm^2.
The 1-s peak flux measured from T0+4 s was
53.1 (+2.0/-2.5) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-2 s to T0+30 s is well fitted by a GRB Band model as follows.
the low-energy photon index alpha: -0.99 (+0.17/-0.11),
the high-energy photon index beta: -2.33 (+0.06/-0.07),
and the peak energy Epeak: 1094 (+131/-175) keV (chi^2/d.o.f = 23.9/23).
Using a redshift of z = 2.27 (Tanvir et al., GCN 14567), we estimate
the isotropic energy release in the 1 keV - 10 MeV range to be
2.55 (+0.12/- 0.11) x10^54 erg and the peak energy at the rest frame
to be 3615 (+532/-469) keV, where cosmological parameters of the Omega
matter, the Omega lambda and the Hubble constant are fixed at 0.27, 0.73
and 70 km/s/Mpc respectively.

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 are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html