GRB 091126A, GRB 091126

H. Hayashi, Y.Nishioka, N. Ohmori, A. Daikyuji,E. Sonoda, K. Kono,
 K. Noda, M. Yamauchi (Univ. of Miyazaki), T. Sugasahara, M. Tashiro, 
 Y. Terada, A. Endo, K. Onda, W. Iwakiri (Saitama U.), 
 S. Sugita(Nagoya U.), K. Yamaoka (Aoyama  Gakuin U.),
 M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
 Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Vasquez (Tokyo Tech.),
 Y. Urata, H.M  Lin (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 GRB 091126A (Fermi/GBM trigger #280915166 ; Tierney et al., 
GCN 10223
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 ) triggered the Suzaku Wide-band  All-sky Monitor (WAM) which 
covers an energy range of 50 keV - 5 MeV at 2009-11-26 07:59:24.67 UT (=T0)

The observed light curve shows a single peak starting at T0 , ending 
at T0+0.5 s with a duration (T90) of about 0.3 seconds.
The fluence in 100 - 1000 keV was 5.76 (-1.72,+1.47) x10^-7 erg/cm^2. 
The 1-s peak flux measured from T0  was 1.57 (-0.84,+0.39) photons/cm^2/s 
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0 to 
T0+0.5 s is well fitted by a single power-law with a photon index 
of 2.27 (-0.43,+0.55) (chi^2/d.o.f. = 20/16).

The power-law with exponential cutoff model also gives a good fit with  
the Epeak of 303(-99,+151) keV, assuming the power-law index of -0.6 as  
was reported by Tierney et al. (GCN 10223
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 ).

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

D. Tierney (UCD) and S. McBreen (UCD/MPE)
report on behalf of the Fermi GBM Team:

"At 07:59:24.76 UT on 26 November 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 091126 (trigger 280915166 / 091126333).
The on-ground calculated location, using the GBM trigger
data, is RA = 83.3, DEC = -19.3 (J2000 degrees,
equivalent to 05 h 33 m, -19 d 18 '), with an uncertainty
of 5.4 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
The angle from the Fermi LAT boresight is 93 degrees.
This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of one pulse
with a duration of about 0.3 s (8-1000 keV).
The time-averaged spectrum from T0-0.256 s to T0+0.256 s is
adequately a power law function with an exponential
high energy cutoff.  The power law index is -0.60 (+0.24/-0.21) and
the cutoff energy, parameterized as Epeak, is 458 (+215/-107) keV
(CSTAT  478 for 476 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(5.9 +/- 0.5)E-7 erg/cm^2. The 0.128 sec peak photon flux measured
starting from T0+0 s in the 8-1000 keV band
is 8.3 +/- 0.7 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."