Modeling dynamical ejecta from binary neutron star mergers and implications for electromagnetic counterparts

TL;DR

This paper provides empirical fits for the properties of ejecta from binary neutron star mergers, aiding the prediction of electromagnetic signals like kilonovae and radio flares based on gravitational wave data.

Contribution

It combines multiple numerical relativity simulations to create models predicting ejecta characteristics and EM counterparts, enhancing the interpretation of GW detections.

Findings

Fits for ejecta mass, energy, and velocity derived from simulations.

Correlations established between binary parameters and EM signals.

Method to estimate kilonova luminosity and lightcurve from binary properties.

Abstract

In addition to the emission of gravitational waves (GWs) the coalescence and merger of two neutron stars will produce a variety of electromagnetic (EM) signals. In this work we combine a large set of numerical relativity simulations performed by different groups and we present fits for the mass, kinetic energy, and the velocities of the dynamical ejected material. Additionally, we comment on the geometry and composition of the ejecta and discuss the influence of the stars' individual rotation. The derived fits can be used to approximate the luminosity and lightcurve of the kilonovae (macronovae) and to estimate the main properties of the radio flares. This correlation between the binary parameters and the EM signals allows in case of a GW detection to approximate possible EM counterparts when first estimates of the masses are available. After a possible kilonovae observation our results could also be used to restrict the region of the parameter space which has to be covered by numerical relativity simulations.