GRB 090411B

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

"At 23:47:44.88 UT on 11 April 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090411B (trigger 261186466 / 090411991).

The on-ground calculated location, using the GBM trigger
data, is RA = 37.0, DEC = 3.2 (J2000 degrees,
equivalent to 02 h 28 m, 3 d 15 '), with an uncertainty
of 2.8 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 111 degrees.

The GBM light curve consists of a single spiky outburst
with a duration (T90) of about 18.7 s (8-1000 keV).
The time-averaged spectrum from T0-2.56 s to T0+20.9 s is
adequately fit by a Band function with Epeak = 189 +/- 37 keV,
alpha = -0.8 +/- 0.1, and beta = -2.0 +/- 0.2
(chi squared 369 for 325 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(8.0 +/- 0.8)E-6 erg/cm^2. The 0.256-sec peak photon flux measured
starting from T0+6.15 s in the 8-1000 keV band
is 7.4 +/- 3.0 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 090411B (Fermi-GBM trigger #261186466/090411991;
 Preece et al., GCN 9131
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triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
 energy range of 50 keV - 5 MeV at 23:47:38 UT (=T0).
The observed light curve shows a multi-peaked structure starting at T0-1s,
ending at T0+25s with a duration (T90) of about 20 seconds.
The fluence in 100 - 1000 keV was 7.6 +/- 0.3 x 10^-6 erg/cm^2.
The 1-s peak flux measured from T0+6s was 2.3 +/- 0.2 photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-1s to
T0+22s is well fitted by a single power-law with a photon index
of 2.4 +/- 0.1 (chi^2/d.o.f = 23.2/21).

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