Signatures of dark-matter accretion on neutron stars in intermediate mass-ratio inspirals

Dense distributions of dark matter around a massive black hole affect the rate of inspiral of a secondary compact object orbiting the primary black hole. For intermediate mass-ratio inspirals, the dominant dark-matter effect arises from dynamical friction acting on the secondary, which accelerates the inspiral relative to a binary in vacuum. A second effect, dark-matter capture onto the secondary (dubbed "secondary accretion"), increases the secondary's mass and influences the binary's evolution. However, secondary accretion depends on the accretion cross-section of dark matter, which also depends on the nature of the compact object and of the dark-matter interactions. Prior work examined accretion when the secondary is a stellar-mass black hole, and it found that accretion can cause substantial gravitational-wave dephasing from vacuum systems. In this talk, I discuss results for a neutron-star secondary with an accretion cross section consistent with interactions of WIMP-like dark matter and neutron-star matter. I find that the effects of accretion in these systems can similarly lead to substantial dephasing of the gravitational-wave signal. These results suggest an avenue to study the interaction between dark and baryonic matter using gravitational-wave observations.