M1 neutrino transport within the numerical-relativistic code BAM with application to low mass binary neutron star mergers

TL;DR

This paper enhances the BAM numerical-relativity code by implementing M1 neutrino transport, enabling detailed simulations of low-mass binary neutron star mergers and their ejecta properties for astrophysical predictions.

Contribution

The authors develop and test a first-order multipolar radiation transport scheme (M1) for neutrinos within the BAM code, advancing the modeling of neutron star mergers.

Findings

Successful implementation and testing of M1 neutrino transport.

Application to low-mass binary systems reveals detailed ejecta properties.

Infrastructure supports integration with kilonova and nucleosynthesis codes.

Abstract

Neutrino interactions are essential for an accurate understanding of the binary neutron star merger process. In this article, we extend the code infrastructure of the well-established numerical-relativity code BAM that until recently neglected neutrino-driven interactions. In fact, while previous work allowed already the usage of nuclear-tabulated equations of state and employing a neutrino leakage scheme, we are moving forward by implementing a first-order multipolar radiation transport scheme (M1) for the advection of neutrinos. After testing our implementation on a set of standard scenarios, we apply it to the evolution of four low-mass binary systems, and we perform an analysis of ejecta properties. We also show that our new ejecta analysis infrastructure is able to provide numerical relativity-informed inputs for the codes $\texttt{POSSIS}$ and $\texttt{Skynet}$, for the computation of kilonova lightcurves and nucleosynthesis yields, respectively.