[vsnet-grb-info 8154] GRB 090715A: Suzaku WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9686
SUBJECT: GRB 090715A: Suzaku WAM observation of the prompt emission
DATE:    09/07/18 10:53:24 GMT
FROM:    Kazutaka Yamaoka at Aoyama Gakuin U  <yamaoka at phys.aoyama.ac.jp>

S. Sugita, K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Suzuki, 
M. Kokubun, T. Takahashi (ISAS/JAXA), M. Tashiro, Y. Terada, 
A. Endo, K. Onda, W. Iwakiri, T. Sugasahara (Saitama U.), 
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, 
E. Sonoda, K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi 
(Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata (NCU), 
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), 
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong 
(Nihon U.), on behalf of the Suzaku WAM team, report:

The short hard GRB 090715A (Swift/BAT trigger #357498; 
Racusin et al., GCN 9666; Baumgartner et al., GCN 9680) 
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an 
energy range of 50 keV - 5 MeV at 2009-07-15 17:25:39.033 UT (=T0). 

The observed light curve shows a multi-peaked structure, starting at 
T0+0.05 s and ending at T0+0.70 s, with a total duration (T90) of about 0.5 s. 
The fluence in 100 - 1000 keV was 1.13(-0.20, +0.08) x10^-6 erg/cm^2.  
The 1-s peak flux measured from T0 s was 2.25(-0.29, +0.12) photons/cm^2/s 
in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0 s to T0+1 s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha:     0.76(-0.46, +0.37), and
  Epeak:     588(-118, +216) keV (chi^2/d.o.f. = 18.1/30).

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

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html