E. Bissaldi (Politecnico & INFN Bari)
reports on behalf of the Fermi GBM Team:
"At 05:06:02.06 UT on 20 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180720A (trigger 553755967 / 180720213),
which was also detected by the AGILE/MCAL (Ursi et al. 2018, GCN 22970).
The on-ground calculated location, using the GBM trigger data, is
RA, Dec = 127.0, -0.4 (J2000 degrees),
with an uncertainty of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic error
which we have characterized as a core-plus-tail model,
with 90% of GRBs having a 3.7 deg error and a small tail
suffering a larger than 10 deg systematic error.
[Connaughton et al. 2015, ApJS, 216, 32]).
The angle from the Fermi LAT boresight at the GBM trigger time is 74 degrees.
The GBM light curve consists of single FRED-like peak
with a duration (T90) of about 9 s (50-300 keV).
The time-averaged spectrum from T0 to T0+10 s is
best fit by a Band function with Epeak = 260 +/- 15 keV,
alpha = -1.08 +/- 0.02 and beta = -2.13 +/- 0.06.
The event fluence (10-1000 keV) in this time interval is
(2.563 +/- 0.026)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.3 s in the 10-1000 keV band
is 36.5 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."