Constraints on bosonic dark matter from observation of old neutron stars

Abstract

Baryon interactions with bosonic dark matter are constrained by the potential for dark-matter-rich neutron stars to collapse into black holes. We consider the effect of dark matter self-interactions and dark matter annihilation on these bounds, and treat the evolution of the black hole after formation. We show that, for nonannihilating dark matter, these bounds extend up to ${m}_{X}\ensuremath{\sim}{10}^{5--7}\text{ }\text{ }\mathrm{GeV}$, depending on the strength of self-interactions. However, these bounds are completely unconstraining for annihilating bosonic dark matter with an annihilation cross section of $⟨{\ensuremath{\sigma}}_{a}v⟩\ensuremath{\gtrsim}{10}^{\ensuremath{-}38}\text{ }\text{ }{\mathrm{cm}}^{3}/\mathrm{s}$. Dark matter decay does not significantly affect these bounds. We thus show that bosonic dark matter accessible to near-future direct detection experiments must participate in an annihilation or self-interaction process to avoid black hole collapse constraints from very old neutron stars.