Abstract
When a stellar massive compact object, such as a black hole, inspirals into an intermediate massive black hole (IMBH), an intermediate-mass-ratio-inspiral (IMRI) system forms. Such kinds of systems are important sources for space-based gravitational wave detectors including LISA, Taiji, and Tianqin. Dark matter (DM) minispikes may form around IMBHs. We study the effect of dynamical friction against a DM minispike on the evolution of eccentric IMRI. For such an investigation we construct the dynamical equations that describe the evolution of eccentric IMRI under the effect of dynamical friction. As dynamical friction is large for small velocity, the dissipation of energy near apastron is more than that near periastron. This greatly enhances the eccentricity. For instance, with an initial semilatus rectum of 1 AU, even a moderate DM minispike can make the eccentricity grow from 0.3 to 0.85. In the extremal case the eccentricity could be enhanced to near 1. We also study a specific case that corresponds to an IMRI in the center of a globular cluster and find the eccentricity can keep its value above 0.95 until the IMRI enters the LISA band. These gravitational wave with enhanced eccentricity by DM minispikes can be easily distinguished from that without DM at due to the eccentricity difference. These anticipations can be tested by future space-based GW detectors such as LISA.
- Received 19 March 2019
DOI:https://doi.org/10.1103/PhysRevD.100.043013
© 2019 American Physical Society