Observable Features of GW170817 Kilonova Afterglow

Adithan Kathirgamaraju; Dimitrios Giannios; Paz Beniamini

doi:10.1093/mnras/stz1564

paper

Observable Features of GW170817 Kilonova Afterglow

arXiv:1901.00868 · doi:10.1093/mnras/stz1564

Abstract

The neutron star merger, GW170817, was followed by an optical-infrared transient (a kilonova) which indicated that a substantial ejection of mass at trans-relativistic velocities occurred during the merger. Modeling of the kilonova is able to constrain the kinetic energy of the ejecta and its characteristic velocity, but not the high-velocity distribution of the ejecta. Yet, this distribution contains crucial information on the merger dynamics. In this work, we assume a power-law distribution of the form $E (> β Γ) \propto (β Γ)^{- α}$ for the energy of the kilonova ejecta and calculate the non-thermal signatures produced by the interaction of the ejecta with the ambient gas. We find that ejecta with minimum velocity $β_{0} ≃ 0.3$ and energy $E \sim 1 0^{51}$ erg, as inferred from kilonova modeling, has a detectable radio, and possibly X-ray, afterglow for a broad range of parameter space. This afterglow component is expected to dominate the observed emission on a timescale of a few years post merger and peak around a decade later. Its light curve can be used to determine properties of the kilonova ejecta and in particular the ejecta velocity distribution $α$ , the minimum velocity $β_{0}$ and its total kinetic energy $E$ . We also predict that an afterglow rebrightening, that is associated with the kilonova component, will be accompanied by a shift of the centroid of the radio source towards the initial position of the explosion.

arXiv comment8 pages, 5 figures, submitted to MNRAS

Observable Features of GW170817 Kilonova Afterglow

Abstract

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