Mapping dynamical ejecta and disk masses from numerical relativity simulations of neutron star mergers

TL;DR

This paper provides new fitting formulas for neutron star merger ejecta and disk masses based on extensive numerical relativity simulations, highlighting the importance of microphysics and neutrino effects.

Contribution

It introduces comprehensive fitting formulas for ejecta and disk properties that incorporate microphysical equations of state and neutrino transport effects.

Findings

Microphysics and neutrino absorption significantly affect ejecta properties.

Microphysical EOS results in lower average ejecta velocities.

Neutrino absorption increases ejecta mass and electron fraction.

Abstract

We present fitting formulae for the dynamical ejecta properties and remnant disk masses from the largest to date sample of numerical relativity simulations. The considered data include some of the latest simulations with microphysical nuclear equations of state (EOS) and neutrino transport as well as other results with polytropic EOS available in the literature. Our analysis indicates that the broad features of the dynamical ejecta and disk properties can be captured by fitting expressions that depend on mass ratio and reduced tidal parameter. The comparative analysis of literature data shows that microphysics and neutrino absorption have a significant impact on the dynamical ejecta properties. Microphysical nuclear equations of state lead to average velocities smaller than polytropic EOS, while including neutrino absorption results in larger average ejecta masses and electron fractions. Hence, microphysics and neutrino transport are necessary to obtain quantitative models of the ejecta in terms of the binary parameters.