GW190814 as a massive rapidly-rotating neutron star with exotic degrees of freedom

TL;DR

This paper explores the possibility that the massive secondary in GW190814 could be a rapidly rotating neutron star with exotic matter like quarks or hyperons, using advanced models that match observational constraints.

Contribution

It introduces a new version of the Chiral Mean Field model with a different quark-deconfinement potential, capable of producing stable stars with pure quark cores and high masses.

Findings

Massive neutron stars (>2.05 Msun) can be modeled with exotic matter.

Rapid rotation can increase stellar mass beyond 2.5 Msun.

Pure quark stars can reach 2.5 Msun with similar baryon content as non-rotating stars.

Abstract

In the context of the massive secondary object recently observed in the compact-star merger GW190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. Our work shows that state-of-the-art relativistic mean field models can generate massive stars reaching $\gtrsim 2.05\,\Msun$, while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and non-standard self-vector interactions are introduced. In particular, we present a new version of the Chiral Mean Field (CMF) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. When rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass $2.5\,\Msun$. We find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the non-rotating stars. This is not the case for pure quark stars, which can easily reach $2.5\,\Msun$ and still possess approximately the same amount of baryons as stable non-rotating stars. We also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event GW190814 can be associated with a star containing quarks as one of its progenitors.