[vsnet-grb-info 8374] GRB 090902B: Suzaku WAM observation of the prompt emission
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Sat Sep 5 13:36:53 JST 2009
TITLE: GCN CIRCULAR
NUMBER: 9897
SUBJECT: GRB 090902B: Suzaku WAM observation of the prompt emission
DATE: 09/09/05 04:36:48 GMT
FROM: Kazutaka Yamaoka at Aoyama Gakuin U <yamaoka at phys.aoyama.ac.jp>
Y. Terada, M. Tashiro, A. Endo, K. Onda, T. Sugasahara,
W. Iwakiri (Saitama U.), K. Yamaoka, S. Sugita (Aoyama Gakuin U.),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji,
E. Sonoda, K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi
(Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata (NCU),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong
(Nihon U.), on behalf of the Suzaku WAM team, report
The Fermi detected long GRB 090902B (Bissaldi et al., GCN 9866,
de Palma et al. GCN 9867) triggered the Suzaku Wide-band All-sky
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at
11:05:08.446 UT (=T0). The observed light curve shows a multi-peaked
structure lasting from T0-0.5 s to T0+24.5 s with a duration (T90) of about
19 seconds. The fluence in 100 - 1000 keV was 1.45 (-0.04, +0.03)x10^-4 erg/cm^2.
The 1-s peak flux measured from T0+14.5 s was 21.3 (-1.3, +0.9) photons/cm^2/s
in the same energy range.
Preliminary result shows that the time-averaged spectrum from
T0-0.5 s to T0+24.5 s is well fitted by a power-law with exponential
cutoff model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha: 0.91 +/- 0.10, and
Epeak: 885 (-38, +39) keV (chi^2/d.o.f. = 25.5/24).
Due to this GRB brightness, a 3% systematcic error was
added for low energy channels. In addition, there might be
some calibration uncertainties in fluence because the GRB
photons came into the WAM through the base plate of the satellite.
All the quoted errors are at 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
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