[vsnet-grb-info 7573] GRB 090410: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9129
SUBJECT: GRB 090410: Suzaku WAM observation of the prompt emission
DATE:    09/04/16 13:21:12 GMT
FROM:    Masanori Ohno at ISAS/JAXA  <ohno at astro.isas.jaxa.jp>

W. Iwakiri, M. Tashiro, Y. Terada, A. Endo, K. Onda,
T. Sugasahara (Saitama U.), Y. Urata (NCU),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo),
K. Yamaoka, S. Sugita (Aoyama Gakuin U.), Y. E. Nakagawa, T. Tamagawa
(RIKEN),
T. Uehara, T. Takahashi, Y. Fukazawa, Y. Hanabata (Hiroshima U.),
E. Sonoda, M. Yamauchi, 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 long GRB 090410 (Swift/BATtrigger #348929 ; Grupe et al.,
GCN 9122) triggered the Suzaku Wide-band  All-sky Monitor (WAM)
 which covers an energy range of 50 keV - 5 MeV at 16:57:53.392 UT
(=T0).

The observed light curve shows  main peaks starting at T0-5s, ending
at T0+25s, followed by a long weak tail seen up to T0+150s. And the
precursor activity reported by Swift/BAT (Barthelmy et al., GCN 9123)
is also seen at T0-55s. The total T90 duration including this precursor
is about 166 seconds. The fluence in 100 - 1000 keV was 1.2 +/- 0.3  x
10^-5 erg/cm^2. The 1-s scaled peak flux measured from T0+5s was 3.0
(-0.3, +0.2)
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-60s to
T0+150s is well fitted by a single power-law with a photon index
of 2.3 (-0.3, +0.3) (chi^2/d.o.f = 4.9/8), and the spectrum of the main
bright peak from T0-5s to T0+25s is well fitted by a power-law with
exponential cutoff model:
 dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
 alpha       1.3 +/-0.5, and
 Epeak       304 (-79, +60) keV (chi^2/d.o.f. = 7.9/7).

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