The Impact of Pions and Muons on Neutron Star Merger Evolution

Neutron star mergers (NSNS) represent one of the most cataclysmic events in astrophysics. From creating rare rapid neutron capture (r-process) elements, to acting as one of the strongest sources of gravitational waves, to creating brilliant electromagnetic afterglows, such as kilonovae, better understanding NSNS dynamics has a wide influence on many areas of astrophysics. While simulations of NSNS continue to advance with increasing supercomputing capabilities, the complex interplay between general relativity, radiation transport, and magnetized fluid flow requires certain approximations to lessen computational cost. To alleviate one such approximation, we consider the often-neglected impact of pions, muons, and trapped neutrinos on the evolution of the NSNS system. While we do not evolve the radiation transport directly, we use arguments of charge neutrality and chemical potential equilibria to approximate the effect of such particles on the nuclear equation of state (EOS). We present the quantitative impact of such considerations on the EOS as well as the effects on NSNS evolution.