Constraints on the astrophysical environment of binaries with gravitational-wave observations

Aims. The dynamics of coalescing compact binaries can be affected by the environment in which the systems evolve, leaving detectable signatures in the emitted gravitational signal. In this paper, we investigate the ability of gravitational-wave detectors to constrain the nature of the environment in which compact binaries merge. Methods. We parametrized a variety of environmental effects by modifying the phase of the gravitational signal emitted by black hole and neutron star binaries. We infer the bounds on such effects by current and future generations of interferometers, studying their dependence on the binary’s parameters. Results. We show that the strong dephasing induced by accretion and dynamical friction can constrain the density of the surrounding medium to orders of magnitude below those of accretion disks. Planned detectors, such as LISA or DECIGO, will be able to probe densities typical of those of dark matter.