Enhancing gravitational waveform models through dynamic calibration.

Current gravitational-wave observations made by Advanced LIGO and Advanced Virgo use theoretical models that predict the signals generated by the coalescence of compact binaries. Detections to date have been in regions of the parameter space where systematic modeling biases have been shown to be small. However, we must now prepare for a future with observations covering a wider range of binary configurations, and ever increasing detector sensitivities placing higher accuracy demands on theoretical models. Strategies to model the inspiral, merger and ringdown of coalescing binaries are restricted in parameter space by the coverage of available numerical-relativity simulations, and when more numerical waveforms become available, substantial efforts to manually (re)calibrate models are required. The aim of this study is to overcome these limitations. We explore a method to combine the information of two waveform models: an accurate, but computationally expensive target model, and a fast but less accurate approximate model. In an automatic process we systematically update the basis representation of the approximate model using information from the target model. The result of this process is a new model which we call the enriched basis. This new model can be evaluated anywhere in the parameter space jointly covered by either the approximate or target model, and the enriched basis model is considerably more accurate in regions where the sparse target signals were available. Here we show a proof-of-concept construction of signals from nonprecessing, spinning black-hole binaries based on the phenomenological waveform family. We show that obvious shortcomings of the previous PhenomB being the approximate model in the region of unequal masses and unequal spins can be corrected by combining its basis with interpolated projection coefficients derived from the more recent and accurate PhenomD as the target model. Our success in building such a model constitutes an major step towards dynamically combining numerical relativity data and analytical waveform models in the computationally demanding analysis of LIGO and Virgo data.