Prospects for Detection of Gravitational Waves from Intermediate-Mass-Ratio Inspirals

We explore prospects for detecting gravitational waves from stellar-mass compact objects spiraling into intermediate mass black holes (BHs) $M\sim 50M_{\odot }$ to $350M_{\odot }$) with ground-based observatories. We estimate a rate for such intermediate-mass-ratio inspirals of $\lesssim 1–30{\mathrm{yr}}^{-1}$ in Advanced LIGO. We show that if the central body is not a BH but its metric is stationary, axisymmetric, reflection symmetric and asymptotically flat, then the waves will likely be triperiodic, as for a BH. We suggest that the evolutions of the waves’ three fundamental frequencies and of the complex amplitudes of their spectral components encode (in principle) details of the central body’s metric, the energy and angular momentum exchange between the central body and the orbit, and the time-evolving orbital elements. We estimate that advanced ground-based detectors can constrain central body deviations from a BH with interesting accuracy.