[vsnet-grb-info 8663] GRB 091109B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10168
SUBJECT: GRB 091109B: Suzaku WAM observation of the prompt emission
DATE:    09/11/14 09:30:39 GMT
FROM:    Masanori Ohno at ISAS/JAXA  <ohno at astro.isas.jaxa.jp>

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


The short GRB 091109B (Swift/BAT trigger #375409 ; Oates et al., GCN  
10148)
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
  energy range of 50 keV - 5 MeV at 2009-11-09 21:49:02.83 UT (=T0).

The observed light curve shows a single peak starting at T0+0.3s, ending
  at T0+0.6s with a duration (T90) of about 0.19 seconds.
The fluence in 100 - 1000 keV was 9.98(-3.69,+0.72) x 10^-7 erg/cm^2.
  The 1-s peak flux measured from T0 was 1.75(-0.59,+0.14) photons/ 
cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0s to T0+1s is well fitted by a power-law with exponential cutoff  
model:
   dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
   alpha       0.91(-0.78,+0.42), and
   Epeak       1330(-610,+1120) keV (chi^2/d.o.f. = 24.6/24).

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