GRB 170423A

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

"At 17:15:08.35 UT on 23 April 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170423A (trigger 514660513 / 170423719).
The on-ground calculated location, using the GBM trigger
data, is RA = 344.34, DEC = -4.26, with an uncertainty
of 1.17 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 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 GBM ground location is 54 degrees.

The GBM light curve consists of several peaks
with a duration (T90) of about 47 s (50-300 keV).
The time-averaged spectrum from T0+2.05 s to T0+49.15 s is
best fit by a Band function with Epeak = 97 +/- 5 keV,
alpha = -1.04 +/- 0.04, and beta = -2.15 +/- 0.04.

The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.8 s in the 10-1000 keV band
is 18.4 +/- 0.4 ph/s/cm^2.

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

Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.),
Peyrot A., Teng J.P. (Les Makes Observatory, France),
Thierry P. (Auragne Observatory, France),
report:

We imaged the field of GRB 170423A detected by Fermi GBM
(trigger 514660513 / 170423719) with the TAROT robotic telescope (D=18cm)
located at the Reunion observatory, France.

The observations started 7.41h after the GRB trigger.
We stacked 6 images of 120s and examined a field of view of 1.2
degree (radius) around the position provided by
Stanbro et al. (GCNC 21030). We do not see any new source
at the limiting magnitude of:

t0+7.41h to t0+7.62h : Rlim=17.8 +/- 0.2

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.