GRB 090411A

Rob Preece (UAH)reports on behalf of the Fermi GBM Team:

"At 20:06:36.89 UT on 4 April, 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090411 (trigger 261173198 / 090411838).

The on-ground calculated location, using the GBM trigger
data, is RA = 159.34, DEC = -68.36 (J2000 degrees,
equivalent to 10 h 37 m, 68 d 21'), with an uncertainty
of 2.3 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 59 degrees.

The GBM light curve consists of two main pulses
with a duration (T90) of about 24.6 s (8-1000 keV).
The time-averaged spectrum from T0-2.04 s to T0+18.4 s is
best fit by a Band function with Epeak = 141 +/- 35 keV,
alpha = -0.88 +/- 0.15, and beta = -1.82 +/- 0.08
(chi squared 319.93 for 318 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(8.6 +/- 1.2)E-6 erg/cm^2. The 0.256-sec peak photon flux measured
starting from T0+11.75 s in the 8-1000 keV band
is 3.25 +/- 0.94 ph/s/cm^2.

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

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

The long GRB 090411A (Fermi-GBM trigger #261173198 ; Preece et al., GCN 9130
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triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
 energy range of 50 keV - 5 MeV at 20:06:36 UT (=T0).
The observed light curve shows a double-peaked structure starting at T0-1s,
ending at T0+20s (T90) of about 16 seconds.
The fluence in 100 - 1000 keV was 7.0 +/-0.6 x 10^-6 erg/cm^2.
The 1-s peak flux measured from T0+12s was 2.5(-0.4,+0.3)
photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-1s to
T0+20s is well fitted by a single power-law with a photon index
of 1.9 (-0.1,+0.2) (chi^2/d.o.f = 9.2/13).

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