[vsnet-grb-info 11956] GRB 120512A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13345
SUBJECT: GRB 120512A: Suzaku WAM observation of the prompt emission
DATE:    12/05/29 01:37:55 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, Y.Tanaka, R. Nakamura, 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 long GRB 120512A (INTEGRAL/IBIS; Mereghetti et al., GCN 13300)
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an 
energy range of 50 keV - 5 MeV at 02:41:43.783 UT (=T0).
The observed light curve shows  a multi-peaked structure starting at 
T0+4 s, ending at T0+24 s,  with a duration (T90) of about 20 seconds. 
The fluence in 100 - 1000 keV was 9.33(-1.13 +0.27) x 10^-6 erg/cm^2. 
The 1-s peak flux measured from T0+9.5s was 2.81(-0.56 +0.26) 
photons/cm^2/s in the same  energy range.

Preliminary result shows that the time-averaged spectrum from T0+4s to 
T0+24s is well fitted by a power-law with exponential cutoff model:
   dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
   alpha       1.05(-0.47 +0.39), and
   Epeak       508.5(-72.2 +114.3) keV (chi^2/d.o.f. = 13.74/24).
We also shows the results with the same spectrum fitted by a GRB Band
model fixing beta of 2.5,　the low-energy photon index alpha: 
-1.03(-0.47 +0.78),　and the peak energy Epeak: 470.5(-85.4 +136.2) keV 
(chi^2/d.o.f = 17.86/24).

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