Amplified capture rate of dark matter in compact binaries and constraints on bosonic dark matter from GW170817

The accretion of dark matter (DM) onto compact objects and the potential gravitational collapse of neutron stars due to this accretion has become a promising indirect probe of DM properties, complementing terrestrial experiments. We show that the accretion flux of DM on stellar objects is amplified in binary systems due to the complex gravitational interaction of said particles with the binary. We perform few-body Monte Carlo simulations to show that this amplification factor is similar to 4-5 for circular binaries, small DM velocity dispersions and mass ratios q greater than or similar to 0.3. We use this factor to improve previous constraints on the scattering cross section of nonannihilating bosonic DM with baryonic matter, and derive upper bounds on this cross section from the observation of the binary NS merger associated with GW170817. We also show that the maximally accretable mass fraction of DM by binary NSs is less than or similar to 10-3, even for extreme DM densities only possible in DM spikes, due to the dynamical friction exerted by the ambient DM.