[vsnet-grb-info 10928] GRB 110903A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12347
SUBJECT: GRB 110903A: Suzaku WAM observation of the prompt emission
DATE:    11/09/16 11:59:17 GMT
FROM:    Yoshitaka Hanabata at Hiroshima U  <hanabata at hep01.hepl.hiroshima-u.ac.jp>

Y. Hanabata, T. Uehara, T. Takahashi, M. Mizuno, M. Ohno, Y. Fukazawa
(Hiroshima U.), T. Yasuda, Y. Terada, M. Tashiro, W. Iwakiri,
K. Takahara, M. Asahina, S. Kobayashi, A. Sakamoto (Saitama U.),
S. Sugita (Nagoya U.), K. Yamaoka (Aoyama Gakuin U.), M. Kokubun,
T. Takahashi (ISAS/JAXA), Y. E. Nakagawa (Waseda U.), N. Ohmori,
M. Akiyama, M. Yamauchi (Univ. of Miyazaki), Y. Urata, P. Tsai,
C-J. Chuang (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo),
on behalf of the Suzaku WAM team, report:

The very long, bright GRB110903A (Mereghetti et al. GCN 12322)
was detected by the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 02:39:34.298 UT (=T0).

The observed light curve shows a multi-peaked structure starting at
T0-57 s, ending at T0+364 s with a duration (T90) of about 340 
secnds. There is a possible precursor at T0-57 s with a duration of
about 15 seconds. The fluence in 100 - 1000 keV was 2.18 (-0.47,
+0.22) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0+198 s was
2.45 (-0.20, +0.17) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0 to
T0+364 s is well fitted by a power-law with exponential cutoff model:
 dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
 alpha : 1.19 (-0.44, +0.54), and
 Epeak : 281 (-78, +33) keV (chi^2/d.o.f. = 39.2/31).
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/untrig/grb_table.html