Model comparison from LIGO-Virgo data on GW170817's binary components and consequences for the merger remnant

TL;DR

This study analyzes GW170817 data to compare neutron star models, finding that many theoretical equations of state remain plausible and that the merger outcome could vary from prompt collapse to stable remnants, with implications for neutron star properties.

Contribution

It performs Bayesian model selection on neutron star equations of state using GW170817 data, providing new constraints and exploring possible merger outcomes.

Findings

Many neutron star models remain consistent with data.

Black hole formation cannot be ruled out based on gravitational waves.

Upper limits on neutron star rotation rates and masses are established.

Abstract

GW170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. We perform Bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. For the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. In addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. We discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. For long-lived remnants, we place an upper limit of 1.9 kHz on the rotation rate. If a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most 3.05 $M_\odot$, and three equations of state considered here can be ruled out. We obtain a tighter limit of 2.67 $M_\odot$ for the case that the merger results in a hypermassive neutron star.