A Computationally Efficient Surrogate Model for Generating High-Accuracy Intermediate to High Mass-Ratio Inspiral Waveforms*

Gravitational wave signals from compact astrophysical sources such as those observed by LIGO and Virgo require a high-accuracy waveform model for signal analysis. Current inspiral-merger-ringdown (IMR) models are calibrated only up to moderate mass ratios, thereby limiting their applicability to signals from high-mass ratio binary systems. We introduce reduced-order surrogate models for gravitational waveforms including several harmonic modes and with mass-ratios varying from 3 to 10,000 and with spin up to 0.8 on the primary black hole, thus vastly expanding the parameter range beyond current surrogate IMR models. Our model is trained on waveforms generated by point-particle black hole perturbation theory (ppBHPT) both for large and comparable mass-ratio binaries. We calibrate the model to spin-aligned numerical relativity simulations in the comparable mass-ratio regime. Our waveforms in the comparable mass-ratio regime agree surprisingly well with those from full numerical relativity after this calibration step. These results will enable data analysis studies in the high-mass ratio regime, including potential intermediate mass-ratio signals from LIGO/Virgo and extreme-mass ratio events of interest to the future space-based observatory LISA.