Paper detail

Radio Flares of Compact Binary Mergers: the Effect of Non-Trivial Outflow Geometry

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.