Cosmic Calipers: Precise and Accurate Neutron Star Radius Measurements with Next-Generation Gravitational Wave Detectors

TL;DR

This paper evaluates how next-generation gravitational wave detectors can significantly improve the precision and accuracy of neutron star radius measurements compared to current detectors, using Bayesian inference and equations of state.

Contribution

It demonstrates that future observatories like the Einstein Telescope and Cosmic Explorer can measure neutron star radii within 5% accuracy, overcoming limitations of current detectors.

Findings

Current detectors have limited radius measurement precision.

Next-generation detectors can achieve <5% radius measurement accuracy.

Choice of mass prior has minimal impact on radius inference.

Abstract

Gravitational waves from merging binary neutron stars carry characteristic information about their astrophysical properties, including masses and tidal deformabilities, that are needed to infer their radii. In this study, we use Bayesian inference to quantify the precision with which radius can inferred with upgrades in the current gravitational wave detectors and next-generation observatories such as the Einstein Telescope and Cosmic Explorer. We assign evidences for a set of plausible equations of state, which are then used as weights to obtain radius posteriors. We find that prior choices and the loudness of observed signals limit the precision and accuracy of inferred radii by current detectors. In contrast, next-generation observatories can resolve the radius precisely and accurately, across most of the mass range to within $\lesssim 5\%$ for both soft and stiff equations of state. We also explore how the choice of the neutron star mass prior can influence the inferred masses and potentially affect radii measurements, finding that choosing an astrophysically motivated prior does not notably impact an individual neutron star's radius measurements.