GCN Circular 9040
Subject
GRB 090327: Fermi GBM detection
Date
2009-03-27T16:32:30Z (15 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 09:41:41.51 UT on 27 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090327 (trigger 259839703 / 090327404).
The on-ground calculated location, using the GBM trigger
data, is RA = 29.5, DEC = -41.6 (J2000 degrees,
equivalent to 01h 58m, -41d 36'), with an uncertainty
of 3.4 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 66 degrees.
The GBM light curve consists of single peak
with a duration (T90) of about 24 s (8-1000 keV).
The time-averaged spectrum from T0 to T0+16.384 s is
well fit by a power law function with an exponential
high energy cutoff. The power law index is -0.50 +/- 0.12 and
the cutoff energy, parameterized as Epeak, is 96.4 +/- 5.1 keV
(chi squared 550 for 475 d.o.f.).
The event fluence (8-1000 keV) in this time interval is
(3.0 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+9.216 s in the 8-1000 keV band
is 3.5 +/- 0.7 ph/s/cm^2.
A Band function fits the spectrum equally well (chi squared 549
for 474 d.o.f.) with Epeak= 89.7 +/- 7.0 keV,
alpha = -0.39 +/- 0.16 and beta = -2.90 +/- 0.45.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."