Constraints on scalar asymmetric dark matter from black hole formation in neutron stars

Abstract

We consider possibly observable effects of asymmetric dark matter (ADM) in neutron stars. Since dark matter does not self-annihilate in the ADM scenario, dark matter accumulates in neutron stars, eventually reaching the Chandrasekhar limit and forming a black hole. We focus on the case of scalar ADM, where the constraints from Bose-Einstein condensation and subsequent black hole formation are most severe due to the absence of Fermi degeneracy pressure. We also note that in some portions of this constrained parameter space, nontrivial effects from Hawking radiation can modify our limits. We find that for scalar ADM with mass between 5 MeV and 13 GeV, the constraint from nearby neutron stars on the scattering cross section with neutrons ranges from ${\ensuremath{\sigma}}_{n}\ensuremath{\lesssim}{10}^{\ensuremath{-}45}\text{ }\text{ }{\mathrm{cm}}^{2}$ to ${10}^{\ensuremath{-}47}\text{ }\text{ }{\mathrm{cm}}^{2}$.