GCN Circular 22689

C. Malacaria (NASA-MFSC/USRA) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At 12:57:09.91 UT on 5 May 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180505A (trigger 547217834 / 180505540).
The on-ground calculated location, using the GBM trigger data, is

RA = 4.51, Dec = -59.89

(J2000 degrees), with an uncertainty of 1.2 degrees (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 124 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 22 s (50-300 keV).
The time-averaged spectrum from T0-3.5 s to T0+31 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.38 +/- 0.03 and
the cutoff energy, parameterized as Epeak, is 235 +/- 19 keV

The event fluence (10-1000 keV) in this time interval is
(2.38 +/- 0.07)E-05 erg/cm^2. The 1-s peak photon flux measured
starting from T0+20.99 s in the 10-1000 keV band
is 29.2 +/- 0.8 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 233 +/- 25 keV, alpha = -1.38 +/- 0.04 and beta = -3.09 +/- 1.32.


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