Self-consistent treatment of thermal effects in neutron-star postmerger remnants: Observational implications for third-generation gravitational-wave detectors

We assess the impact of accurate, self-consistent modeling of thermal effects in neutron-star merger remnants in the context of third-generation gravitational-wave detectors. This is done through the usage, in Bayesian model selection experiments, of numerical-relativity simulations of binary neutron star (BNS) mergers modeled through (i) nuclear, finite-temperature (or ``tabulated'') equations of state (EOSs), and (ii) their simplifed piecewise (or ``hybrid'') representation using seven or ten polytropic pieces. These cover four different EOSs, namely SLy4, DD2, HShen and LS220. Our analyses make direct use of the Newman-Penrose scalar ψ₄ outputted by numerical simulations. Considering a detector network formed by three Cosmic Explorers, we show that differences in the gravitational-wave emission predicted by the two models are detectable with a natural logarithmic Bayes factor logB≥5 at average distances of dL50 Mpc, reaching dL100 Mpc for source inclinations ι≤0.8, regardless of the EOS. This impact is most pronounced for the HShen EOS. For low inclinations, only the DD2 EOS prevents the detectability of such modeling differences at dL150 Mpc. Our results suggest that the usage a self-consistent treatment of thermal effects is crucial for third-generation gravitational-wave detectors.