[vsnet-grb-info 7357] GRB 090301B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8922
SUBJECT: GRB 090301B: Fermi GBM detection
DATE:    09/03/01 16:38:46 GMT
FROM:    Andreas von Kienlin at MPE  <azk at mpe.mpg.de>

A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: 

"At 07:33:37.98 UT on 01 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090301B (trigger 257585619 / 090301315 ).
The on-ground calculated location, using the GBM trigger 
data, is RA = 350.3, DEC = 9.0 (J2000 degrees, 
equivalent to 23h 21m, 09d 00'), with an uncertainty 
of 4.2 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 56 degrees.

The GBM light curve shows a single peak lasting about 5 s 
superimposed on a lower-level continuum.
The burst duration (T90) is about 28 s (8-1000 keV)
The time-averaged spectrum from T0-1.536 s to T0+3.584 s is 
well fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.03 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 546 +/- 133 keV
(chi squared 703.17 for 731 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(2.69 +/- 0.13)E-06 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+1.536 s in the 8-1000 keV band 
is 4.4 +/- 0.1 ph/s/cm^2.

A Band function fits the spectrum equally well 
(chi squared 700.28 for 730 d.o.f.) with Epeak= 427 +/- 147 keV, 
alpha = -0.98 +/- 0.12 and beta = -1.93 +/- 0.24. 

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