[vsnet-grb-info 20867] GRB 180718B: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22965
SUBJECT: GRB 180718B: Fermi GBM detection
DATE:    18/07/19 14:07:31 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007 at uah.edu>

R. Hamburg (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 18:18:24.46 UT on 18 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180718B (trigger 553630709 / 180718763).
which was also detected by the Fermi LAT (Racusin et al. 2018, GCN 22961).
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 48
degrees.

The GBM light curve shows a structured FRED-like peak
with a duration (T90) of about 98 s (50-300 keV).
The time-averaged spectrum from T0+0 s to T0+66 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.73 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 761 +/- 78 keV.
A Band function also fits the spectrum with Epeak = 731 +/- 83 keV,
alpha = -0.71 +/- 0.05,and beta = -2.79 +/- 0.73.

The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.6 s in the 10-1000 keV band
is 3.6 +/- 0.2 ph/s/cm^2.

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