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GCN Circular 22875

Subject
GRB 180630A: Fermi GBM detection
Date
2018-06-30T16:54:15Z (6 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH), A. von Kienlin (MPE), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 11:11:54.41 UT on 30 June 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180630A (trigger 552049919 / 180630467)
which was also detected by the Swift BAT and XRT instruments
(D'Avanzo et al. 2018, GCN 22872).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 20
degrees.

The GBM light curve consists of a single structured peak
with a duration (T90) of about 12 s (50-300 keV).
The time-averaged spectrum from T0-1.54s to T0+8.70 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.37 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 84 +/- 8 keV.
A Band function fits the spectrum equally well
with Epeak = 60 +/- 10 keV, alpha = -1.11 +/- 0.20,
and beta = -2.32 +/- 0.16.

The event fluence (10-1000 keV) in this time interval is
(2.5 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.15 s in the 10-1000 keV band
is 9.4 +/- 0.4 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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