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GCN Circular 16850

GRB 140928A: Fermi GBM detection
2014-09-29T11:18:44Z (10 years ago)
Andreas von Kienlin at MPE <>
A. von Kienlin (MPE) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 10:29:53.55 UT on 28 September 2014, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 140928A (trigger 433592996  / 140928437) which 
was also detected by Fermi/LAT (Desiante et al. 2014, GCN 16847) and Swift
(Pagani et al. 2014, GCN 16848). The GBM on-ground location is consistent 
with the LAT/Swift position.

The angle from the Fermi LAT boresight is 110 degrees.

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

The GBM light curve shows a structured pulse 
with a duration (T90) of about 14 s (50-300 keV).
The time-averaged spectrum from T0-3.072 s to T0+8.192 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.12 +/- 0.13  and
the cutoff energy, parameterized as Epeak, is 732 +/- 72 keV.

The event fluence (10-1000 keV) in this time interval is
1.02 +/- 0.04)E-05 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+5.12  s in the 10-1000 keV band
is 4.8 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak= 671 +/- 82 keV, 
alpha = -0.05 (+0.16/-0.13) and beta = -2.6 (+0.3/-0.4).

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