[vsnet-grb-info 7229] GRB 090109: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8802
SUBJECT: GRB 090109: Fermi GBM detection
DATE:    09/01/12 22:30:25 GMT
FROM:    Elisabetta Bissaldi at MPE  <ebs at mpe.mpg.de>

E. Bissaldi(MPE) and A. von Kienlin (MPE)
report on behalf of the Fermi GBM Team:


"At 07:58:29.49 UT on Day Month Year, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090109 (trigger 253180711 / 090109332).
The on-ground calculated location, using the GBM trigger
data, is RA = 122.8, DEC = +54.8 (J2000 degrees,
equivalent to 08h 11m, 54d 48'), with an uncertainty
of 12.5 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 62 degrees.

This weak GRB consists of a single peak
with a duration (T90) of about 5 s (8-1000 keV).
The time-averaged spectrum from T0-2.8 s to T0+1.3 s is
well fit by a simple power law function with 
index -1.50 +/- 0.08 (chi squared 236 for 241 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.21 +/- 0.05)E-06 erg/cm^2. The 1.3-sec peak photon flux measured
starting from T0 in the 8-1000 keV band
is 2.76 +/- 0.16 ph/s/cm^2.


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