[vsnet-grb-info 10160] GRB 110120A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11609
SUBJECT: GRB 110120A: Suzaku WAM observation of the prompt emission
DATE:    11/01/28 14:57:51 GMT
FROM:    Yuji Urata at Nat. Central U.  <urata at astro.ncu.edu.tw>

P. Tsai, Y. Urata (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, S. Hong, W. Iwakiri, K. Takahara,
T. Yasuda (Saitama U.), M. Ohno, M. Serino, 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), 
on behalf of the Suzaku WAM team, report:


The log GRB 110120A (Fermi/GBM trigger 317231981 / 110120666 ; Lin et
al., GCN 11591; Omodei et al., GCN 11597) triggered the Suzaku
Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV
- 5 MeV at 2011/01/20 15:59:39.22 UT (=T0).

The observed light curve shows a multi-peaked structure starting at
T0-0.7s, ending at T0+8s, with a duration (T90) of about 6.4
seconds. The fluence in 100 - 1000 keV was 2.32 (+/-0.16) x 10^-5
ergs/cm^2. The 1-s peak flux measured from T0+0.38s was 30.40
(+/-0.93) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-0.7s
to T0+8s is well fitted by a power-law with exponential cutoff
model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       1.34 (-0.51, +0.40), and
  Epeak       418.60 (-84.64, +110.46) keV (chi^2/d.o.f. = 39.92/40).


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