  Over the past three years, the fading non-thermal emission from the GW170817
remained generally consistent with the afterglow powered by synchrotron
radiation produced by the interaction of the structured jet with the ambient
medium. Recent observations by Hajela et al. (2021) indicate the change in
temporal and spectral behaviour in the X-ray band. We show that the new
observations are compatible with the emergence of a new component due to
non-thermal emission from the fast tail of the dynamical ejecta of ab-initio
binary neutron star (BNS) merger simulations. This provides a new avenue to
constrain binary parameters. Specifically, we find that equal mass models with
a soft equation of state (EOS) and high mass ratio models with stiff EOS are
disfavored as they typically predict afterglows that peak too early to explain
the recent observations. Moderate stiffness and mass ratio models, instead,
tend to be in a good overall agreement with the data.
