[vsnet-grb-info 7561] GRB 090409: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9119
SUBJECT: GRB 090409: Fermi GBM detection
DATE:    09/04/09 17:03:04 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

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


"At 06:54:01.44 UT on 09 April 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090409 (trigger 260952843 / 090409288).

The on-ground calculated location, using the GBM trigger
data, is RA = 302.1, DEC = +1.1 (J2000 degrees,
equivalent to 20h 08m, 01d 06'), with an uncertainty
of 7.9 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 90 degrees.

This weak and long GRB consists of a single peak
with a duration (T90) of about 20 s (8-1000 keV).
The time-averaged spectrum from T0 to T0+5.1 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is 1.2 +/- 0.7 and
the cutoff energy, parameterized as Epeak, is 137 +/- 17 keV
(chi squared 346 for 356 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(6.14 +/- 0.26)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4 s in the 8-1000 keV band
is 1.36 +/- 0.14 ph/s/cm^2.


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