GRB 090602

Elisabetta Bissaldi (MPE) reports on behalf of the Fermi GBM Team:


"At 13:32:22.85 UT on 02 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090602 (trigger 265642344 / 090602564).
The on-ground calculated location, using the GBM trigger
data, is RA =  248.9, DEC = -65.0 (J2000 degrees,
equivalent to 16h 36m, -65d 00'), with an uncertainty
of 3.4 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 112 degrees.

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

The GBM light curve consists of a broad single peak
with a duration (T90) of about 16 s (8-1000 keV).
The time-averaged spectrum from T0-1.3s to T0+9s is
best fit by a power law function with an exponential
high energy cutoff. The power law index is -0.56 +/- 0.14 and
the cutoff energy, parameterized as Epeak, is 503 +/- 91 keV
(chi squared 327 for 358 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(5.7 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.8 s in the 8-1000 keV band
is 3.62 +/- 0.17 ph/s/cm^2.


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

N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, K. Noda, A. Daikyuji, 
Y. Nishioka, M. Yamauchi (Univ. of Miyazaki),
M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA),
K. Yamaoka, S. Sugita (Aoyama Gakuin U.), Y. E. Nakagawa,
T. Tamagawa (RIKEN), 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 090602 (Fermi-GBM trigger 265642344 / 090602564;
Bissaldi et al., GCN9486
Loading...
 
 ) triggered the Suzaku Wide-band All-sky 
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV
at 13:32:23.291 UT (=T0).

The observed light curve shows a bright multi-peaked structure
starting at T0-1 s, ending at T0+12 s. 
The total T90 duration is about 10 seconds.

The fluence in 100 - 1000 keV was 3.7 (-1.6, +0.4) x10-6 erg/cm2.
The 1-s peak flux measured from T0+3s was 1.0 (-0.7, +0.3)
photons/cm2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-1s to T0+11s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       0.79(-0.79, +0.95), and
  Epeak        581(+954,-195) keV (chi2/d.o.f. = 52.9/45).

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