On the nature of the mass-gap object in the GW190814 event

TL;DR

This paper investigates whether the mass-gap object in GW190814 could be a degenerate star, exploring various models including hadronic, quark, and hybrid stars, and assessing their compatibility with observational constraints.

Contribution

It provides a comprehensive analysis of different stellar models to determine the nature of the GW190814 mass-gap object, considering hyperons, quark matter, and hybrid configurations.

Findings

Mass-gap object could be a hadronic, quark, or hybrid star.

Certain parameter choices favor specific star types.

None of the models can be definitively ruled out.

Abstract

In this work, we make a very extensive study on the conditions that allow the mass-gap object in the GW190814 event to be faced as a degenerate star instead of a black hole. We begin revisiting some parametrizations of the Quantum Hadrodynamics (QHD) and then study under which conditions the hyperons are present in such a massive star. Afterward, using a vector MIT based model, we study if self-bound quark stars, satisfying the Bodmer-Witten conjecture fulfill all the observational constraints. Finally, we study hybrid stars within a Maxwell construction and check for what values of the bag, as well as the vector interaction, a quark core star with only nucleons, and with nucleons admixed with hyperons can reach at least 2.50 M$_\odot$. We conclude that, depending on the choice of parameters, none of the possibilities can be completely ruled out, i.e., the mass-gap object can be a hadronic (either nucleonic or hyperonic), a quark, or a hybrid star. However, some cases are more probable than others.