[vsnet-grb-info 19996] GRB 171102A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22083
SUBJECT: GRB 171102A: Fermi GBM detection
DATE:    17/11/02 15:51:46 GMT
FROM:    Matthew Stanbro at UAH/Fermi  <mcs0001 at uah.edu>

M. Stanbro (UAH), C. Meegan (UAH), and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At 02:33:35.99 UT on 02 November 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 171102A (trigger 531282820 / 171102107)
which was also detected by the Fermi-LAT (M. Yassine et al. 2017, GCN 22081)
The GBM on-ground location is consistent with the LAT position.

The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux of the GRB.
This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight to
the LAT location is 43 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 35 s (50-300 keV).
The time-averaged spectrum from T0+20.48 s to T0+56.32 s is
best fit by a Band function with Epeak = 171 +/- 6 keV,
alpha = -0.82 +/- 0.02, and beta = -2.59 +/- 0.14.

The event fluence (10-1000 keV) in this time interval is
(2.88 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+49.2 s in the 10-1000 keV band
is 28.7 +/- 0.3 ph/s/cm^2.

A power law function with an exponential high-energy cutoff
fits the spectrum equally well.  The power law index is -0.87 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 187 +/- 4 keV.

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