GCN Circular 8922
Subject
GRB 090301B: Fermi GBM detection
Date
2009-03-01T16:38:46Z (16 years ago)
From
Andreas von Kienlin at MPE <azk@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."