[vsnet-grb-info 11961] GRB 120519A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13350
SUBJECT: GRB 120519A: Suzaku WAM observation of the prompt emission
DATE:    12/05/30 07:29:10 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

A. Sakamoto, M. Tashiro, Y. Terada, W. Iwakiri, T. Yasuda, K. Takahara,
M. Asahina, S. Kobayashi, H. Ueno (Saitama U.),
M. Akiyama, N. Ohmori, M. Yamauchi (Univ. of Miyazaki),
K. Yamaoka, Y. E. Nakagawa (Waseda U.),
Y. Hanabata, T. Kawano, K. Takaki, R. Nakamura, Y.Tanaka, M. Ohno,
Y. Fukazawa (Hiroshima U.), S. Sugita (Nagoya U.), M. Kokubun,
T. Takahashi (ISAS/JAXA), Y. Urata, P. Tsai (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report:

The short GRB 120519A (IPN; Pal'shin et al., GCN 13313, Konus-Wind;
Golenetskii et al., GCN 13315) triggered the Suzaku Wide-band All-sky 
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 
17:18:14.64 UT (=T0).

The observed light curve shows a multi-peaked structure starting at
T0-0.2 s, ending at T0+0.6 s, with a duration (T90) of about 0.72 
seconds. The fluence in 100 - 1000 keV was 1.45(-0.28 +0.09) x 10^-6 
erg/cm^2. The 1-s peak flux measured from T0-0.5s was 2.76(-0.33 +0.18) 
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-0.5s to
T0+0.5s is well fitted by a power-law with exponential cutoff model:
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha 0.41(-0.41 +0.58), and Epeak 736(-141 +226) keV
(chi^2/d.o.f. = 16.9/24).

In case we fit the same spectrum by a GRB Band model with a fixed
beta of 2.5, the best fit parameters and their errors are,
low-energy photon index alpha: -0.10(-0.92 +1.60),
and the peak energy Epeak: 611(-146 +279) keV (chi^2/d.o.f = 20.0/24).


All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

----
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