Frequency-domain gravitational waves from non-precessing black-hole binaries. I. New numerical waveforms and anatomy of the signal (1508.07250v2)

Abstract: In this paper we discuss the anatomy of frequency-domain gravitational-wave signals from non-precessing black-hole coalescences with the goal of constructing accurate phenomenological waveform models. We first present new numerical-relativity simulations for mass ratios up to 18 including spins. From a comparison of different post-Newtonian approximants with numerical-relativity data we select the uncalibrated SEOBNRv2 model as the most appropriate for the purpose of constructing hybrid post-Newtonian/numerical-relativity waveforms, and we discuss how we prepare time-domain and frequency-domain hybrid data sets. We then use our data together with results in the literature to calibrate simple explicit expressions for the final spin and radiated energy. Equipped with our prediction for the final state we then develop a simple and accurate merger-ringdown-model based on modified Lorentzians in the gravitational wave amplitude and phase, and we discuss a simple method to represent the low frequency signal augmenting the TaylorF2 post-Newtonian approximant with terms corresponding to higher orders in the post-Newtonian expansion. We finally discuss different options for modelling the small intermediate frequency regime between inspiral and merger-ringdown. A complete phenomenological model based on the present work is presented in a companion paper.

• The paper introduces advanced numerical-relativity simulations of non-precessing black-hole binaries, extending calibration to mass ratios up to 18 while incorporating spin effects.
• The paper constructs hybrid waveforms by matching post-Newtonian approximants with numerical data, identifying the SEOBNRv2 model as a reliable tool.
• The paper provides analytical fits for predicting the final spin and radiated energy, refining the frequency-domain anatomy of waveform signals during the merger-ringdown phase.

Overview of Frequency-Domain Gravitational Waves from Non-Precessing Black-Hole Binaries

The paper "Frequency-domain gravitational waves from non-precessing black-hole binaries. I. New numerical waveforms and anatomy of the signal" presents significant strides in the modeling of gravitational-wave (GW) signals emanating from non-precessing black-hole binary mergers. The authors introduce new numerical-relativity simulations and explore the anatomy of GW signals to develop accurate phenomenological waveform models suitable for data analysis in gravitational-wave astronomy.

Key Contributions

1. Numerical Waveform Simulations:
   • The authors present new numerical-relativity (NR) simulations of black-hole binary mergers with mass ratios reaching up to 18, which include effects of spin. These simulations extend the range of calibration for current waveform models, providing critical benchmarks for modeling high mass ratio and spinning binaries.
2. Hybrid Waveform Construction:
   • The paper constructs hybrid waveforms by matching post-Newtonian (PN) approximants with numerical relativity data. The uncalibrated SEOBNRv2 model is identified as the most suitable PN approximant for constructing these hybrids, offering a more reliable option for waveform calibration.
3. Modeling the Final State:
   • The paper provides analytical fits for predicting the final spin and radiated energy of a black-hole merger, key components for accurate GW signal modeling. Using a combination of numerical data and theoretical insights, the authors present simple yet comprehensive models for predicting the final state, considering the symmetric mass ratio and effective spin.
4. Waveform Anatomy:
   • The anatomy of waveform signals is meticulously analyzed across the frequency domain. The authors refine the representation of amplitude and phase in the frequency domain, incorporating higher-order PN terms and leveraging insights from the merger-ringdown processes.
5. Merger-Ringdown Phase:
   • A modified Lorentzian model is proposed for the merger-ringdown phase of the waveform, improving upon previous models by addressing their high-frequency fall-off limitations. This allows for a more accurate description of the phase and amplitude immediately post-merger.
6. Implications for Gravitational-Wave Astronomy:
   • This work underpins more precise models for GW search algorithms and parameter estimation techniques, enhancing the interpretative frameworks employed in observatories like LIGO and Virgo. By extending the range of modeled phenomena to higher mass ratios and spin configurations, this research supports future discoveries of more diverse binary black hole systems across the universe.

Implications and Future Directions

The paper's findings have direct implications for enhancing the accuracy of waveform models used in GW data analysis, particularly for high-mass-ratio and high-spin systems. As the authors suggest, the results offer a pathway to replace previous PhenomB and PhenomC models, furnishing the GW community with a tool that balances computational efficiency with high fidelity.

The authors hint at future directions, including generalizing the approach to include higher harmonics and precessing binaries. Such advancements would further expand the predictive power and utility of the proposed models in the search for gravitational waves.

This paper is a pivotal addition to the accumulating efforts to harness gravitational-wave data, thereby deepening our understanding of the universe's most extreme astrophysical events. As GW detection and analysis continue to mature, the methodologies and insights encapsulated in this paper will surely play an instrumental role in decoding the mysteries encapsulated within these cosmic signals.