[vsnet-grb-info 8855] GRB 100116A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10353
SUBJECT: GRB 100116A: Suzaku WAM observation of the prompt emission
DATE:    10/01/21 13:06:25 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.)
K. Yamaoka (Aoyama Gakuin U.), S. Sugita (Nagoya U),
Y. Terada, M. Tashiro, A. Endo, K. Onda, T. Sugasahara, W. Iwakiri (Saitama 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, H. M. Lin (NCU),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong
(Nihon U.), on behalf of the Suzaku WAM team, report:

The long GRB 100116A (Fermi/GBM trigger #285370262 / 100116.89 
Briggs et al., GCN 10330, McEnery et al., GCN 10333) triggered the Suzaku 
Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV 
at 21:31:00.15 UT (=T0).

The observed light curve shows two separated pulses, a precursor at T0+0 to T0+4 sec 
and a main harder pulse at T0+81 to T0+111 sec, and the duration (T90) was about 
96 seconds. The fluences in 100 - 1000 keV were 1.24(-0.16, +0.17) e-6 and 2.89 (-0.08, +0.06) e-5 erg/cm^2 
in the precursor and the main pulse, respectively. The 1-s peak flux measured from T0+94 s
was 7.26 (-0.43, +0.47) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0+81 s to T0+111 s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha      1.15 (-0.10, +0.09), and
  Epeak      1119 (-135, +137) keV (chi^2/d.o.f. = 79.0/54).

Due to the brightness of this burst, a 3% systematic error
was added for low energy channels.
All the quoted errors are at 90% confidence level.

The light curves of this event are available at the following URL:
 http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html

-- 

 Takeshi Uehara  (Hiroshima Univ.)
 E-mail: uehara at hep01.hepl.hiroshima-u.ac.jp