Gravitational wave surrogate model for spinning, intermediate mass ratio binaries based on perturbation theory and numerical relativity

We present BHPTNRSur2dq1e3, a reduced order surrogate model of gravitational waves emitted from binary black hole (BBH) systems in the comparable to large mass ratio regime with aligned spin (₁) on the heavier mass (m₁). We trained this model on waveform data generated from point particle black hole perturbation theory (ppBHPT) with mass ratios varying from 31000 and spins from -0. 8₁0. 8. The waveforms are 13, 500 m₁ long and include all 4 spin-weighted spherical harmonic modes except the (4, 1) and m=0 modes. We find that, for binaries with ₁-0. 5, retrograde quasinormal modes are significantly excited, thereby complicating the modeling process. To overcome this issue, we introduce a domain decomposition approach to model the inspiral and merger-ringdown portion of the signal separately. The resulting model can faithfully reproduce ppBHPT waveforms with a median time-domain mismatch error of 810^-5. We then calibrate our model with numerical relativity (NR) data in the comparable mass regime (310). By comparing with spin-aligned BBH NR simulations at q=15, we find that the dominant quadrupolar (subdominant) modes agree to better than 10^-3 (10^-2) when using a time-domain mismatch error, where the largest source of calibration error comes from the transition-to-plunge and ringdown approximations of perturbation theory. Mismatch errors are below 10^-2 for systems with mass ratios between 615 and typically get smaller at larger mass ratio. Our two models---both the ppBHPT waveform model and the NR-calibrated ppBHPT model---will be publicly available through gwsurrogate and the black hole perturbation toolkit packages.