[AAVSO-HEN] GRB 090306C: Fermi GBM detection

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  8960
SUBJECT: GRB 090306C: Fermi GBM detection
DATE:    09/03/09 14:59:13 GMT
FROM:    Arne Rau at MPE  <arau at mpe.mpg.de>

Arne Rau (MPE) reports on behalf of the Fermi GBM Team:

"At 05:52:05.35 UT on 06 March 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090306C (trigger 258011527  / 090306245).

The on-ground calculated location, using the GBM trigger
data, is RA = 135.0, DEC = +51.7 (J2000 degrees,
equivalent to 09 h 00 m, 51 d 36 '), with an uncertainty
of 5.5 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 14 degrees.

The GBM light curve shows one main peak lasting about 5s followed by a 
broader tail
with a total duration (T90) of about 38.8 s (8-1000 keV).
The time-averaged spectrum from T0-4.096 s to T0+6.144 s is
adequately fit by a power law function with an exponential
high energy cutoff at 107 +/- 16 keV and  with index -0.58 +/- 0.29
(chi squared 380 for 381 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(9.0 +/- 2.2)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.024 s in the 8-1000 keV band
is 2.4 +/- 0.1 ph/s/cm^2.

A Band function fits the spectrum equally well (chi squared 378 for 380 
d.o.f.)
with Epeak= 87 +/- 25 keV, alpha = -0.32 +/- 0.54 and beta = -2.28 +/-0.43.

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