GCN Circular 11988
Subject
GRB 110428A: Suzaku WAM observation of the prompt emission
Date
2011-05-02T10:21:42Z (13 years ago)
From
Makoto Tashiro at Saitama U/Swift <tashiro@phy.saitama-u.ac.jp>
W. Iwakiri, Y. Terada, M. Tashiro, K. Takahara, T. Yasuda (Saitama U.),
T. Uehara, Y. Hanabata, T. Takahashi, Y. Fukazawa (Hiroshima U.),
N. Vasquez (Tokyo Tech.) K. Yamaoka (Aoyama Gakuin U.),
M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA),
S. Sugita (Nagoya U.), Y. E. Nakagawa (Waseda U.),
N. Ohmori, M. Akiyama, M. Yamauchi (Univ. of Miyazaki),
Y. Urata, P. Tsai (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo),
on behalf of the Suzaku WAM team, report:
The long bright GRB 110428A localized by Fermi-LAT (Vasileiou et al.,
GCN 11982) was observed the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 09:18:30 UT (=T0).
The observed light curve shows double-peaked structure starting at
T0-2s, ending at T0+10 s with a duration (T90) of about 5 seconds. The
fluence in 100 - 1000 keV was 1.31 (-0.43, +2.03) x 10^-5 erg/cm^2.
The 1-s peak flux measured from T0+4 s was
9.91 (-0.34, +1.19) photons/cm^2/s in the same energy range.
Preliminary result shows that the time-averaged spectrum from
T0-2s to T0+10s is well fitted by a power-law with exponential cutoff
model :
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha 1.11 (-0.22, +0.19), and Epeak 195.5 (-14.4, +15.9) keV
(chi2/d.o.f. = 15.8/20).
All the quoted errors are at statistical 90% confidence level.