The Influence of Muons, Pions, and Trapped Neutrinos on Neutron Star Mergers

TL;DR

This study uses advanced simulations to explore how muons, pions, and neutrinos influence neutron star mergers, revealing significant effects on gravitational wave signals and merger dynamics.

Contribution

It systematically incorporates muons, pions, and neutrinos into neutron star merger models, providing new insights into their impact on merger outcomes.

Findings

Frequency shifts of 100-200 Hz in gravitational waves due to microphysics

Microphysical degrees of freedom affect merger thermodynamics

Enhanced modeling accuracy for neutron star mergers

Abstract

The merger of two neutron stars probes dense matter in a hot, neutrino-trapped regime. In this work, we investigate how fully accounting for pions, muons, and muon-type neutrinos in the trapped regime may affect the outcome of the merger. By performing fully general-relativistic hydrodynamics simulations of merging neutron stars with equations of state to which we systematically add those different particle species, we aim to provide a detailed assessment of the impact of muons and pions on the merger and post-merger phase. In particular, we investigate the merger thermodynamics, mass ejection and gravitational wave emission. Our findings are consistent with previous expectations, that the inclusion of such microphysical degrees of freedom and finite temperature corrections leads to frequency shifts on the order of 100-200 Hz in the post-merger gravitational wave signal, relative to a fiducial cold nucleonic equation of state model.