[vsnet-grb-info 16594] GRB 150523A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17875
SUBJECT: GRB 150523A: Suzaku WAM observation of the prompt emission
DATE:    15/05/27 07:29:45 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

T. Fujinuma,  M. Tashiro, Y. Terada, T. Yasuda, S. Takeda,
T. Nagayoshi, J. Enomoto, S. Nakaya, S. Matsuoka, S. Yabe (Saitama U.),
M. Yamauchi, N. Ohmori, R. Kinoshita (Univ. of Miyazaki),
W. Iwakiri (RIKEN), K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.),
M. Ohno, T. Kawano, Y. Fukazawa (Hiroshima U.),
Y. E. Nakagawa, M. Kokubun, T. Takahashi (ISAS/JAXA),
Y. Urata (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo)
on behalf of the Suzaku WAM team, report:

The long GRB 150523A(Fermi GBM trigger: Yu et al.,GCN 17863;
Fermi-LAT detection:Bissaldi et al.,GCN 17864;
Konus-Wind observation: Golenetskii et al.,GCN 17870) triggered the 
Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range
of 50 keV - 5 MeV at 09:29:50 UT (=T0).

The observed light curve shows double-peaked structure starting at
T0-4 s, ending at T0+33 s, with a duration (T90) of about 32 seconds.
The fluence in 100 - 1000 keV was 1.81(+0.23/-0.25) x 10^-5 erg/cm^2.
The 1-s peak flux measured from T0+31 s was
3.52(+0.19/-0.34) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-4s
to T0+33s is well fitted by a power-law with exponential cutoff model:
dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha    0.70(+0.48/-0.56), and
Epeak    417(+56/-41) keV (chi^2/d.o.f. = 61.26/52).

All the quoted errors are at statistical 90% confidence level.

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