[vsnet-grb-info 7994] GRB 090618: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9535
SUBJECT: GRB 090618: Fermi GBM observation
DATE:    09/06/19 22:55:39 GMT
FROM:    Sheila McBreen at MPE  <smcbreen at mpe.mpg.de>

Sheila McBreen (UCD/MPE)
reports on behalf of the Fermi GBM Team:

"At 08:28:26.66 UT on 18 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090618 (trigger 267006508 / 090618353)
which was also detected by Swift/BAT (Schady et al. 2009, GCN 9512)
and AGILE (Longo et al. 2009, GCN 9524).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 133 degrees.

The GBM light curve consists of 4 pulses
with a duration of about 155 s (8-1000 keV).
The time-averaged spectrum from T0 to T0+140 s is
adequately fit by a Band function with Epeak = 155.5 (+11.1/-10.5) keV,
alpha = -1.26 (+0.06/-0.02), and beta = -2.50 (+0.15/-0.33).
We observe significant spectral evolution within the fitted
time interval.

The event fluence (8-1000 keV) in this time interval is
(2.70 +/- 0.06)E-4 erg/cm^2.  Using standard cosmology
(Omega_matter = 0.27, Omega_lambda = 0.73, H0=71)
and the reported redshift of 0.54 (Cenko et al. 2009, GCN 9518)
the isotropic equivalent energy in the 8-1000 keV band is
E_iso = 2.0E+53 erg.

The 1-sec peak photon flux measured starting from T0+63 s
in the 8-1000 keV band is  73.4 +/- 2.0 ph/s/cm^2.

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