[vsnet-grb-info 7881] GRB 090522 : Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9425
SUBJECT: GRB 090522 : Fermi GBM detection
DATE:    09/05/27 12:46:59 GMT
FROM:    Sheila McBreen at MPE  <smcbreen at mpe.mpg.de>

Sheila McBreen (UCD/MPE) and Andreas von Kienlin (MPE)
report on behalf of the Fermi GBM Team:

"At 08:15:49.33 UT on 22 May 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090522 (trigger 264672951 / 090522344).

The on-ground calculated location, using the GBM trigger
data, is RA = 277.7, DEC = +19.6 (J2000 degrees,
equivalent to 18 h 31 m, +19 d 36 '), with an uncertainty
of 4.9 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 53 degrees.

The GBM light curve consists of one pulse
with a duration (T90) of about 22 s (8-1000 keV).
The time-averaged spectrum from T0-2 s to T0+20 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.03 (+ 0.41 / -0.53) and
the cutoff energy, parameterized as Epeak, is 75.8 (+36.9 / -15.9) keV
(chi squared 615 for 603 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.2 +/- 0.3)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2 s in the 8-1000 keV band
is 3.5 +/- 0.2 ph/s/cm^2.

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