  For the first time, a short gamma-ray burst (GRB) was unambiguously
associated with a gravitational wave (GW) observation from a binary neutron
star (NS) merger. This allows us to link the details of the central engine
properties to GRB emission models. We find that photospheric models (both
dissipative and non-dissipative variants) have difficulties accounting for the
observations. Internal shocks give the most natural account of the observed
peak energy, viewing angle and total energy. We also show that a simple
external shock model can reproduce the observed GRB pulse with parameters
consistent with those derived from the afterglow modeling. We find a simple
cocoon shock breakout model is in mild tension with the observed spectral
evolution, however it cannot be excluded based on gamma-ray data alone. Future
joint observations of brighter GRBs will pose even tighter constraints on
prompt emission models.
