Quantifying modeling uncertainties when combining multiple gravitational-wave detections from binary neutron star sources

TL;DR

This study assesses how waveform model uncertainties impact the precision of neutron-star radius measurements from multiple gravitational-wave detections, highlighting the importance of controlling systematic biases for accurate nuclear matter constraints.

Contribution

It provides a comprehensive simulation-based quantification of waveform systematics in neutron-star radius inference from multiple gravitational-wave signals.

Findings

Statistical uncertainty in neutron-star radius can be as low as ±250 meters.

Systematic differences between waveform models can be twice as large as statistical uncertainties.

Controlling waveform systematics is crucial for accurate neutron-star equation of state inference.

Abstract

With the increasing sensitivity of gravitational-wave detectors, we expect to observe multiple binary neutron-star systems through gravitational waves in the near future. The combined analysis of these gravitational-wave signals offers the possibility to constrain the neutron-star radius and the equation of state of dense nuclear matter with unprecedented accuracy. However, it is crucial to ensure that uncertainties inherent in the gravitational-wave models will not lead to systematic biases when information from multiple detections are combined. To quantify waveform systematics, we perform an extensive simulation campaign of binary neutron-star sources and analyse them with a set of four different waveform models. Based on our analysis with about 38 simulations, we find that statistical uncertainties in the neutron-star radius decrease to $\pm 250\rm m$ ($2\%$ at $90\%$ credible interval) but that systematic differences between currently employed waveform models can be twice as large. Hence, it will be essential to ensure that systematic biases will not become dominant in inferences of the neutron-star equation of state when capitalizing on future developments.