Gravitational-wave signatures of dark-matter capture in intermediate mass-ratio inspirals

When particle dark matter (DM) is bound gravitationally around a massive black hole (BH) in sufficiently high densities, the DM will affect the rate of inspiral of a secondary compact object that forms a binary with the massive BH. For intermediate mass-ratio inspirals (IMRIs), the dominant difference from inspirals in vaccum arises from dynamical friction acting on the secondary. However, if the secondary is a stellar-mass BH, then it can capture some of the DM as it inspirals in the DM distribution and increase in mass. Prior work (assuming a static DM distrubtion during the inspiral) showed that DM capture has a subdominant effect compared to that of dynamical friction, but it can still be large enough to cause substantial dephasing of these systems from those in vacuum and those with DM where the effect of just dynamical friction was modeled. In this talk, I will revisit these prior estimates of the impact of DM capture on the emitted gravitational waves from IMRIs of binary BHs. I will show there is a region of parameter space of binaries for which estimates of the capture were too large (specifically, because the DM distribution was assumed to be unchanging throughout the inspiral, thereby allowing the secondary BH to capture more mass in DM than that enclosed within the orbit of the secondary). To restore consistency in these scenarios, I will discuss a method to evolve the DM distribution such that the mass captured by the secondary never exceeds the enclosed mass.