Incorporating a radiative hydrodynamics scheme in the numerical-relativity code BAM

TL;DR

This paper enhances a numerical-relativity code to include nuclear physics and neutrino effects, enabling more accurate simulations of binary neutron star mergers and their observable signals.

Contribution

The paper introduces an updated BAM code with nuclear equations of state and a neutrino leakage scheme for improved neutron star merger simulations.

Findings

Stable and accurate evolution of binary neutron star systems with different equations of state.

Good agreement of simulation results with existing literature.

Validation through tests of neutrino-induced gravitational collapse.

Abstract

To study binary neutron star systems and to interpret observational data such as gravitational-wave and kilonova signals, one needs an accurate description of the processes that take place during the final stages of the coalescence, e.g., through numerical-relativity simulations. In this work, we present an updated version of the numerical-relativity code BAM in order to incorporate nuclear-theory based Equations of State and a simple description of neutrino interactions through a Neutrino Leakage Scheme. Different test simulations, for stars undergoing a neutrino-induced gravitational collapse and for binary neutron stars systems, validate our new implementation. For the binary neutron stars systems, we show that we can evolve stably and accurately distinct microphysical models employing the different equations of state: SFHo, DD2, and the hyperonic BHB$\Lambda \phi$. Overall, our test simulations have good agreement with those reported in the literature.