# Neutron-star Radius from a Population of Binary Neutron Star Mergers

## TL;DR

This paper demonstrates that gravitational-wave observations of binary neutron star mergers can accurately measure neutron-star radii by combining inspiral and postmerger data, achieving 10% precision for a large sample.

## Contribution

It introduces analytical fits to postmerger waveforms for multiple equations of state and uses quasi-universal relations to improve radius measurement accuracy.

## Key findings

- Neutron-star radius can be measured with a few percent accuracy.
- Analytical fits to postmerger waveforms are developed for the first time.
- Measuring radius within 10% is feasible for 100 binaries between 100-300 Mpc.

## Abstract

We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies we utilize analytical fits to postmerger numerical-relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass. We further exploit quasi-universal relations to derive errors in compactness from those frequencies. Measuring the average radius to well within 10% is possible for a sample of 100 binaries distributed uniformly in volume between 100 and 300 Mpc, so long as the equation of state is not too soft or the binaries are not too heavy.