[vsnet-grb-info 9566] GRB 100728A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11037
SUBJECT: GRB 100728A: Suzaku WAM observation of the prompt emission
DATE:    10/08/02 15:27:24 GMT
FROM:    Yuji Urata at Nat. Central U.  <urata at astro.ncu.edu.tw>

P. Tsai, Y. Urata, H.M. Lin (NCU), T. Uehara, Y. Hanabata, T. Takahashi, Y.
Fukazawa (Hiroshima U.), N. Vasquez (Tokyo Tech.) K. Yamaoka (Aoyama Gakuin U.),
S. Sugita (Nagoya U.), Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, 
T. Yasuda (Saitama U.), M. Ohno, M. Suzuki, M. Kokubun, 
T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, T. Tamagawa (RIKEN), 
N. Ohmori, A. Daikyuji, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki), 
K. Nakazawa, K. Makishima (Univ. of Tokyo),
S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:


The long GRB 100728A (Fermi/GBM trigger #301976252; von Kienlin et al., GCN
#11006; Swift/BAT trigger #430151; Cannizzo et al., GCN 11004) triggered the
Suzaku Wide-band  All-sky Monitor (WAM) which covers an energy range of 50
keV - 5 MeV at 2010-07-28 02:17:32.68 UT (=T0).

The observed light curve shows a multi-peaked structure starting at T0-5s,
ending at T0+198s, with a duration (T90) of about 162 seconds. The fluence
in 100 - 1000 keV was 9.09 (-1.55, +0.07) x 10^-5 ergs/cm^2. The 1-s peak
flux measured from T0+80s was 4.66 (-0.78, +0.03) photons/cm^2/s in the same
energy range.

Preliminary result shows that the time-averaged spectrum from
T0-2s to T0+180s is well fitted by a power-law with exponential cutoff
model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       0.76 (+/-0.11), and
  Epeak       378 (-14, +13) keV (chi^2/d.o.f. = 34.4/22).

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