[vsnet-grb-info 9524] GRB 100724B: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10995
SUBJECT: GRB 100724B: Suzaku WAM observation of the prompt emission
DATE:    10/07/26 15:09:31 GMT
FROM:    Takeshi Uehara at Hiroshima U  <uehara at hirax7.hepl.hiroshima-u.ac.jp>

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), Y. Urata, H. M. Lin, P. Tsai (NCU), 
K. Nakazawa, K. Makishima (Univ. of Tokyo),
S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:


The bright long GRB 100724B (Fermi/GBM trigger #301624927 ; P. N. Bhat et al., GCN 10977) 
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an 
energy range of 50 keV - 5 MeV at 00:42:04.70 UT (=T0). 

The observed light curve shows a multi-peaked structure starting at T0-7s, ending 
at T0+143s with a duration (T90) of about 103 seconds. 
The fluence in 100 - 1000 keV was 1.63(+0.03/-0.07) x 10^-4 erg/cm^2.  
The 1-s peak flux measured from T0+65s was 9.3 photons/cm^2/s in the same 
energy range.

Preliminary result shows that the time-averaged spectrum from
T0-4.1s to T0+141.3s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       1.09	 (+0.18/-0.19), and
  Epeak       666	 (+107/-67) keV (chi^2/d.o.f. = 22.8/22).

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

The light curves with 1-sec time resolution for this burst will be appeared at:
 http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html