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GCN Circular 9686

Subject

GRB 090715A: Suzaku WAM observation of the prompt emission

Date

2009-07-18T10:53:24Z (15 years ago)

From

Kazutaka Yamaoka at Aoyama Gakuin U <yamaoka@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 9666Not found
 
 
; Baumgartner et al., GCN 9680Not found
 
 
) 
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