We explore the prospects for identifying differences in simulated
gravitational-wave signals of binary neutron star (BNS) mergers associated with
the way thermal effects are incorporated in the numerical-relativity modelling.
We consider a hybrid approach in which the equation of state (EoS) comprises a
cold, zero temperature, piecewise-polytropic part and a thermal part described
by an ideal gas, and a tabulated approach based on self-consistent,
microphysical, finite-temperature EoS. We use time-domain waveforms
corresponding to BNS merger simulations with four different EoS. Those are
injected into Gaussian noise given by the sensitivity of the third-generation
detector Einstein Telescope and reconstructed using BayesWave, a Bayesian
data-analysis algorithm that recovers the signals through a model-agnostic
approach. The two representations of thermal effects result in frequency shifts
of the dominant peaks in the spectra of the post-merger signals, for both the
quadrupole fundamental mode and the late-time inertial modes. For some of the
EoS investigated those differences are large enough to be told apart,
especially in the early post-merger phase when the signal amplitude is the
loudest. These frequency shifts may result in differences in the inferred tidal
deformability, which might be resolved by third-generation detectors up to
distances of about tens of Mpc at most.
Future Roadmap: Identifying Differences in Gravitational-Wave Signals of Binary Neutron Star (BNS) Mergers
Introduction
In this study, we investigate the prospects of identifying differences in simulated gravitational-wave signals of binary neutron star (BNS) mergers. We focus on the incorporation of thermal effects in numerical-relativity modeling and explore how different approaches to representing thermal effects can impact the resulting waveforms. Our analysis includes four different equations of state (EoS) and utilizes time-domain waveforms injected into Gaussian noise.
Hybrid Approach vs Tabulated Approach
We consider two approaches for incorporating thermal effects: a hybrid approach and a tabulated approach.
- The hybrid approach consists of a cold, zero temperature, piecewise-polytropic part of the equation of state (EoS) and a thermal part described by an ideal gas.
- The tabulated approach is based on a self-consistent, microphysical, finite-temperature EoS.
Data Analysis with BayesWave
We utilize BayesWave, a Bayesian data-analysis algorithm, to reconstruct the gravitational-wave signals. BayesWave follows a model-agnostic approach, allowing us to recover the signals without imposing specific waveform models.
Results: Frequency Shifts in Post-Merger Signals
Our analysis reveals that the two representations of thermal effects result in frequency shifts of the dominant peaks in the spectra of the post-merger signals. These frequency shifts are observed for both the quadrupole fundamental mode and the late-time inertial modes. The differences in frequency shifts are particularly significant in the early post-merger phase when the signal amplitude is the loudest.
Implications for Inferred Tidal Deformability
The observed frequency shifts may lead to differences in the inferred tidal deformability. Third-generation detectors, such as the Einstein Telescope, have the potential to resolve these differences. However, the ability to differentiate between different equations of state based on these frequency shifts is limited to distances of about tens of Mpc at most.
Conclusion: Challenges and Opportunities Ahead
The identification of differences in gravitational-wave signals of BNS mergers associated with the incorporation of thermal effects presents both challenges and opportunities in the field. Further research is needed to refine our understanding of the impact of thermal effects on waveform characteristics and the extraction of physical parameters. The development of more advanced data analysis techniques and the construction of next-generation detectors will provide valuable tools to tackle these challenges and explore new opportunities in gravitational-wave astronomy.