[vsnet-grb-info 21286] GRB 181027A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23385
SUBJECT: GRB 181027A: Fermi GBM detection
DATE:    18/10/27 19:12:34 GMT
FROM:    Peter Veres at UAH  <veresp at gmail.com>

P. Veres (UAH) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At 01:49:47.31 UT on 27 October 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 181027A (trigger 56229779 / 181027076),
which was also detected by the Swift/BAT (Lien et al. 2018, GCN 23383).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 61
degrees.

The GBM light curve consists of two pulses
with a duration (T90) of about 90 s (50-300 keV).
The time-averaged spectrum from T0-84.5 s to T0+44.5 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.10 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 183 +/- 27 keV.

The event fluence (10-1000 keV) in this time interval is
(7.76 +/- 0.57)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.64 s in the 10-1000 keV band
is 2.48 +/- 0.22 ph/s/cm^2.

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