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 EOS 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.
Highlights
In this paper we considered numerical relativity datasets available in the literature for the dynamical ejecta properties and the remnant disk mass from binary neutron star mergers
We performed a simple statistical analysis of the ejecta parameters that highlighted that the ejecta parameters are subjected to large systematic uncertainties, partially due to different treatment of neutrinos, in addition to the equations of state (EOS) formulations
Low order polynomials in these quantities provide a simple description of the data available and favorably compare to the other options in terms of sum of squared residuals when only models of M0RefSet are considered as well or models from all datasets
Summary
The UV/optical/NIR transient AT2017gfo [1,2,3,4,5,6,7,8,9,10,11,12,13,14], counterpart of the gravitational-wave signal GW170817 [15,16,17,18], is explained as the kilonova signal from the radioactive decay of r-process elements synthesized in the mass ejected during binary neutron star mergers [10, 19,20,21,22,23,24,25,26,27,28,29,30,31,32]. Minimal models of the kilonova AT2017gfo require at least two ejecta components to account for the observed light curves: a lanthanide-poor (for the blue signal) and a lanthanide-rich (for the red signal) one [10, 28,29,30,31,32] These components are often identified as the dynamical ejecta and the wind ejecta from the remnant disk, simulations clearly indicate that this interpretation is not complete. They can be used to identify the main parametric dependencies of the ejecta mechanisms; on the other hand, they can be employed to constrain the source parameters from kilonova observations, e.g., [31, 71,72,73] They are key to predict the amount and the properties of the ejecta that enter chemical evolution models, e.g.,[74]. We use CGS units except for masses and velocities, given in units of M and c, respectively
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