  In addition to producing a strong gravitational signal, a short gamma-ray
burst (GRB), and a compact remnant, neutron star mergers eject significant
masses at significant kinetic energies. This mass ejection takes place via
dynamical mass ejection and a GRB jet but other processes have also been
suggested: a shock-breakout material, a cocoon resulting from the interaction
of the jet with other ejecta, and viscous and neutrino driven winds from the
central remnant or the accretion disk. The different components of the ejected
masses include up to a few percent of a solar mass, some of which is ejected at
relativistic velocities. The interaction of these ejecta with the surrounding
interstellar medium will produce a long lasting radio flare, in a similar way
to GRB afterglows or to radio supernovae. The relative strength of the
different signals depends strongly on the viewing angle. An observer along the
jet axis or close to it will detect a strong signal at a few dozen days from
the radio afterglow (or the orphan radio afterglow) produced by the highly
relativistic GRB jet. For a generic observer at larger viewing angles, the
dynamical ejecta, whose contribution peaks a year or so after the event, will
generally dominate. Depending on the observed frequency and the external
density, other components may also give rise to a significant contribution. We
also compare these estimates with the radio signature of the short GRB 130603B.
The radio flare from the dynamical ejecta might be detectable with the EVLA and
the LOFAR for the higher range of external densities $n\gtrsim 0.5{\rm
cm^{-3}}$.
