[vsnet-grb-info 7527] GRB 090401A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9085
SUBJECT: GRB 090401A: Suzaku WAM observation of the prompt emission
DATE:    09/04/04 08:27:36 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

M. Suzuki, M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA),
N. Kodaka, W. Iwakiri, M. Tashiro, Y. Terada, Y. Urata, A. Endo,
K. Onda, K. Morigami, T. Sugasahara (Saitama U.), T. Enoto,
K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita, K. Yamaoka
(Aoyama Gakuin U.), 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.), N. Vasquez
(Tokyo Tech.), on behalf of the Suzaku WAM team, report:

The bright long GRB090401A (Swift/BAT trigger #348128; Schady et al., 
GCN 9062; Sato et al., GCN 9064) was detected by the the Suzaku Wide-band 
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV 
at 00:02:34.509 UT (=T0).

The observed light curve shows a multi-peaked structure lasting from 
T0-5s to T0+38s.  There is also a weak precursor starting at ~T0-103s, 
 resulting in the total duration (T90) of about 112 seconds.
The fluence in 100 - 1000 keV was 1.37(-0.10,+0.08) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+27s was 5.1(-0.4,+0.5) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-5s to
T0+38s is fitted by a single power-law with a photon index
of 2.14 (-0.13,+0.14) (chi^2/d.o.f = 21.4/24).
3 % systematic errors were included in low energy channels. 
All the quoted errors are at 90% confidence level. 

The light curves with 1-sec time resolution for this burst will be appeared at:
 http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html