Optimized Radio Follow Up of Binary Neutron-Star Mergers

Dario Carbone, Alessandra Corsi

Published 2018-01-08Version 1

Motivated by the recent discovery of the binary neutron-star (BNS) merger GW170817, we determine the optimal observational setup for detecting and characterizing nearby (d_L~40 Mpc) radio counterparts of BNS mergers. We simulate GW170817-like radio transients, and radio afterglows generated by fast jets with isotropic energy E_iso~10^50 erg, expanding in a low-density interstellar medium (ISM; n_ISM=10^-4-10^-2 cm^-3), observed from different viewing angles (from slightly off-axis to largely off-axis). We then determine the optimal timing of GHz radio observations following the precise localization of the BNS, assuming a sensitivity comparable to that of the Karl G. Jansky Very Large Array. We show that radio is the optimal band to explore the fastest ejecta from BNSs in low-density ISM, since the optical emission is likely to be dominated by the so-called "kilonova" component, while X-rays from the jet are detectable only for a small subset of the BNS models considered here. Finally, we discuss how future radio arrays like the next generation VLA (ngVLA) would improve the detectability of BNS mergers with physical parameters similar to the ones here explored.