Detectability of radio afterglows from binary neutron star mergers and implications for fast radio bursts

ABSTRACT Binary neutron star (BNS) mergers are one of the proposed origins for both repeating and non-repeating fast radio bursts (FRBs), which associates FRBs with gravitational waves and short gamma-ray bursts (GRBs). In this work, we explore detectability of radio afterglows from BNS mergers and compare it to the observed radio limits on FRB afterglow. We calculate the afterglow flux powered by the two components: a relativistic jet and a slower isotropic ejecta, and quantify the detection probability as a function of the source redshift, observing time, and flux sensitivity. The model parameter distributions inferred from short GRB afterglows are adopted, and viewing angle distributions (uniform spherical, gravitational-wave, on-axis biased) are assumed to reflect different searching scenario. Assuming that FRBs are not strongly beamed, we make comparison to FRBs detected with reported radio limits and find the detection probabilities are 1–10 per cent in general, and hence not a strong constraint on the BNS progenitor model considering the small sample number (20 per cent at 10 μJy sensitivity) for the isotropic component that would peak around ∼1–10 yr after the merger. Therefore, a long-term radio monitoring of persistent radio emission for these objects is important.