  The next generation gravitational waves (GW) detectors are most sensitive to
GW emitted by compact (neutron star/black hole) binary mergers. If one of those
is a neutron star the merger will also emit electromagnetic radiation via three
possible channels: Gamma-ray bursts and their (possibly orphan) afterglows
(Eichler et al. 1989), Li-Paczynski Macronovae (Li & Paczynski 1998) and radio
flares (Nakar & Piran 2011). This accompanying electromagnetic radiation is
vitally important in confirming the GW detections (Kochanek & Piran 1993). It
could also reveal a wealth of information regarding the merger and will open a
window towards multi-messenger astronomy. Identifying and characterizing these
counterparts is therefore of utmost importance. In this work we explore late
time radio flares emitted by the dynamically ejected outflows. We build upon
previous work and consider the effect of the outflow's non-trivial geometry.
Using an approximate method we estimate the radio light-curves for several
ejected matter distributions obtained in numerical simulations. Our method
provides an upper limit to the effect of non-sphericity. Together with the
spherical estimates the resulting light curves bound the actual signal. We find
that while non-spherical geometries can in principle lead to an enhanced
emission, in most cases they result in an increase in the timescale compared
with a corresponding spherical configuration. This would weaken somewhat these
signals and might decrease the detection prospects.

High Energy Astrophysical Phenomena