GRB 090623

Arne Rau (MPE) reports on behalf of the Fermi GBM Team:

"At 02:34:17.56 UT on 23 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090623 (trigger 267417259 / 090623107).

The on-ground calculated location, using the GBM trigger
data, is RA = 309.0deg, DEC = -43.2 deg (J2000 degrees,
equivalent to 20 h 36 m, -43 d 12 '), with an uncertainty
of 2.0 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 73 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of at least five peaks
with a duration (T90) of about 72.2 s (8-1000 keV).
The time-averaged spectrum from T0-1.920 s to T0+40.064 s is
best fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.73 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 476 +/- 39 keV
(chi squared 738 for 655 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(9.60 +/- 0.02)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+0.003 s in the 8-1000 keV band
is 3.30 +/- 0.04 ph/s/cm^2.

A Band function fits the spectrum equally well (chi squared 737 for 654 
d.o.f.)
with Epeak= 428 +/- 51 keV, alpha = -0.69 +/- 0.05 and beta = -2.3 +/- 0.4.

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

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),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka,
S. Sugita (Aoyama Gakuin U.), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.),
Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
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),
on behalf of the Suzaku WAM team,
report:

The long GRB 090623 (Fermi/GBM trigger 267417259 / 090623107, Rau et al.,
GCN 9566
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 ) was detected by the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 02:34:17.04 UT (=T0). The observed
light curve shows a multi-peaked structure lasting from T0-2 s, ending at
T0+48 s, with a duration (T90) of about 38 seconds. 

The fluence in 100 - 1000 keV was 2.7 (-0.9, +0.2) * 10^-5 ergs/cm^2.
The 1-s peak flux measured from T0+0.5 s was 5.3 (-1.2, +0.3) photons/cm^2/s 
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-2 s to T0+48 s
is well fitted by a power-law with an exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha        1.0(-0.3, +0.3), and
  Epeak        601(-100, +147) keV (chi2^/d.o.f. = 15/18).
 
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
 
The light curves for this burst is available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html