[vsnet-grb-info 7875] GRB 090518: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9419
SUBJECT: GRB 090518: Fermi GBM detection
DATE:    09/05/22 16:29:30 GMT
FROM:    Bill Paciesas at UAH  <bill.paciesas at nasa.gov>

W. Paciesas (UAH) reports on behalf of the Fermi GBM Team:

"At 01:54:44.52 UT on 18 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090518 (trigger 264304486 / 090518080).
which was also detected by the SWIFT-BAT
(Evans et al. 2009, GCN 9386)
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 53 degrees.

The GBM light curve consists of a single asymmetric peak
with a duration (T90) of about 9 s (8-1000 keV).
The time-averaged spectrum from T0-2.048 s to T0+7.04 s is
adequately fit by a simple power law function with index -1.59 +/- 0.06
(chi squared 688 for 688 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.60 +/- 0.05)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.64 s in the 8-1000 keV band
is 4.7 +/- 0.1 ph/s/cm^2.

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