Dark neutron stars from a heavy dark sector

Abstract

We study the formation and properties of dark neutron stars in a scenario where dark matter is made up of (heavy) dark baryons in a sequestered copy of the MSSM. This scenario naturally explains the coincidence of baryonic and dark matter abundances without the need for tuning particle masses. In particular, the supersymmetry breaking scales in the visible and dark sectors may differ by up to 10-11 orders of magnitude. We argue that dark neutrons should be the lightest dark baryons, but that dark protons may be cosmologically long lived. This allows a small fraction of dark matter to remain ionized until the first halos start to form, providing cooling mechanisms that foster the gravitational collapse and fragmentation of sub-halo structures, ultimately resulting in dark neutron star and black hole formation. For a wide range of model parameters, we find dark neutron stars with generally smaller mass and radius than ordinary visible sector neutron stars. We also discuss their potential detectability, particularly through gravitational microlensing and dark magnetic dipole radiation at radio frequencies through photon-dark photon kinetic mixing.