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GCN Circular 9020

Subject
GRB 090320B: Fermi GBM detection.
Date
2009-03-23T15:39:21Z (15 years ago)
From
Narayana Bhat at U Alabama/Huntsville/GBM <Narayana.Bhat@nasa.gov>
P. N. Bhat (UAH) 
report on behalf of the Fermi GBM Team:

At 19:13:46.10 UT on 20 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090320B (trigger 259269228 / 090320801).

The on-ground calculated location, using the GBM trigger
data, is RA = 183.8, DEC = 57.6 (J2000 degrees,
equivalent to 12 h 15.3 m, 57 d 33 '), with an uncertainty
of 9.6 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 101 degrees.

The GBM light curve shows one main pulse with several
weaker trailing pulses with a duration (T90) of about 52 s (8-1000 keV).
The time-averaged spectrum from T0-7.4 s to T0+52 s is
adequately fit by a power law function with an exponential
high energy cutoff.  The power law index is -1.1 +/- 0.3 and
the cutoff energy, parameterized as Epeak, is 72 +/- 14 keV

(chi squared 255 for 237 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0 s in the 8-1000 keV band
is 0.12 +/- 0.04 ph/s/cm^2.

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