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GCN Circular 8902

GRB 090217: Fermi GBM detection
2009-02-17T16:47:38Z (15 years ago)
Andreas von Kienlin at MPE <>
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: 

"At 04:56:42.56 UT on 17 February 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090217 (trigger 256539404/ 090217206).

The on-ground calculated location, using the GBM trigger 
data, is RA = 211.9, DEC = -2.8  (J2000 degrees, 
equivalent to 14h 08m, -02d 48'), with an uncertainty 
of 1.0 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 34 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve shows one major structured peak with a 
duration (T90) of about 32.8 s (8-1000 keV) and (T50) of 
about 4.6 s (8-1000 keV). 
The time-averaged spectrum from T0+0.003  s to T0+19.584 s is 
well fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.85 +/- 0.02 and 
the cutoff energy, parameterized as Epeak, is 626 +/- 29 keV 
(chi squared 631.30 for 482 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(3.08 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured 
starting from T0+6.272 s in the 8-1000 keV band 
is 11.2 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well (chi squared 629.43 for
481d.o.f.) with Epeak= 610 +/- 32 keV, alpha = -0.845 +/- 0.023 and 
beta = -2.86 +/- 0.36. 

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