Binary Mergers of Neutron Star and Mirror Neutron Stars

A potential dark matter candidate is the twin Higgs model known as mirror matter, which is identical to the standard model but the particle masses are heavier. Recent work [1] explored the idea of mirror neutron stars based on creating a crust to core standard model equation of state and using Lattice Quantum Chromodynamics to scale the particle masses and interactions. It was found that mirror neutron stars are significantly smaller and denser than standard model neutron stars.

Because mirror matter only interacts with the standard model through the gravitational force, mirror neutron stars can only be detected through gravitational observations. A merger between a standard model neutron star and a mirror neutron star will not interact in the same manner as a binary of standard model neutron stars.  In this work, we use a two-fluid Tolman–Oppenheimer–Volkoff equation to study the mass-radius relation after a merger between a standard model neutron star and a mirror neutron star.  We find that if these stars were to merge then the resulting object either becomes a black hole or has an even smaller mass-radius than the original mirror neutron star.

[1] M. Hippert, J. Setford, H. Tan, D. Curtin, J. Noronha-Hostler and N. Yunes, "Mirror Neutron Stars," [arXiv:2103.01965 [astro-ph.HE]]