Role of muons in binary neutron star mergers: First simulations
Henrique Gieg, Federico Schianchi, Maximiliano Ujevic, Tim Dietrich
Abstract
In this work, we present a set of binary neutron star (BNS) merger simulations including the net muon fraction as an additional degree of freedom in the equation of state (EOS) and hydrodynamics evolution using the numerical-relativity code BAM. Neutrino cooling is modeled via a neutrinos leakage scheme, including in-medium corrections to the opacities and emission rates of semileptonic charged-current reactions, although within the elastic approximation. We show that, for our particular choice of baseline baryonic EOS, the presence of muons delays the gravitational collapse of the remnant compared to the case where muons are neglected. Furthermore, when muons and muonic weak reactions are considered, no gravitational collapse occurs within our simulation time and muons are confined in the densest portions of the remnant, while the disk is effectively colder, less protonized and demuonized. Accordingly, ejecta properties are affected; e.g., ejecta masses are systematically smaller for the muonic setups and exhibit a larger fraction of neutron-rich, small velocity material. Overall, our results suggest that the inclusion of muons and muon-flavored neutrino reactions in the context of BNS merger simulations should not be neglected, thus representing an important step toward more realistic modeling of such systems.