[vsnet-grb-info 7393] GRB 090305C: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8957
SUBJECT: GRB 090305C: Suzaku WAM observation of the prompt emission
DATE:    09/03/09 09:36:28 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

GRB 090305C: Suzaku WAM observation of the prompt emission

W. Iwakiri, M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda,
N. Kodaka, K. Morigami, T. Sugasahara (Saitama U.),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita,
K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Kokubun, M. Suzuki,
T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, T. Tamagawa (RIKEN),
T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata (Hiroshima U.),
E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono,
H. Hayashi, (Univ. of Miyazaki), S. Hong (Nihon U.),
on behalf of the Suzaku WAM team, report:

The IPN localized short GRB 090305C (Golenetskii et al., GCN 8941)
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 17:19:38.326 UT (=T0).

The observed light curve shows a multi-peaked structure starting at T0
+0.2s, ending at T0+1.3s with a duration (T90) of about 0.9 seconds.
The fluence in 100 - 1000 keV was 1.85(-0.58, +0.13)x 10^-06 erg/cm2.
The 0.5-s scaled peak flux measured from T0+0s was 4.13(-0.97, +0.19)
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0+0s
to T0+1.5s is fitted by a power-law with exponential cutoff model:

dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha	1.05(-0.49, 0.38), and
Epeak	835 ( -237, 618) keV (chi^2/d.o.f. = 5.20/13).

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

The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html