[AAVSO-HEN] GRB 090620: Fermi GBM detecion

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  9554
SUBJECT: GRB 090620: Fermi GBM detecion
DATE:    09/06/22 15:11:42 GMT
FROM:    Arne Rau at MPE  <arau at mpe.mpg.de>

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

"At 09:36:23.47 UT on 20 June 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090620 (trigger 267183385 / 090620400).

The on-ground calculated location, using the GBM trigger
data, is RA = 237.4 deg, DEC = 61.2 deg (J2000 degrees,
equivalent to 15 h 50 m, 61 d 12 '), 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 60 degrees.

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

The GBM light curve shows a single peak
with a duration (T90) of about 16.5 s (8-1000 keV).
The time-averaged spectrum from T0-0.003 s to T0+16.640 s is
best fit by a Band function with Epeak = 156 +/- 6 keV,
alpha = -0.40 +/- 0.04, and beta = -2.44 +/- 0.10
(chi squared 576 for 532 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(6.6 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+4.352 s in the 8-1000 keV band
is 7.0 +/- 0.3 ph/s/cm^2.

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