Probing the nuclear equation of state from the existence of a $\sim 2.6~M_{\odot}$ neutron star: the GW190814 puzzle

TL;DR

This paper investigates the nuclear equation of state using the GW190814 event, exploring constraints from neutron star rotation, the speed of sound, and tidal deformability to understand the nature of the compact object.

Contribution

It systematically analyzes the implications of the GW190814 event for the nuclear equation of state, considering rotation, speed of sound limits, and tidal deformability constraints.

Findings

Constraints on the nuclear EoS from neutron star rotation assumptions.

Tidal deformability sensitivity to dense matter properties.

Potential existence of high-mass neutron stars in the universe.

Abstract

On August 14, 2019, the LIGO/Virgo collaboration observed a compact object with mass $\sim 2.59_{-0.09}^{+0.08}~M_{\odot}$, as a component of a system where the main companion was a black hole with mass $\sim 23~M_{\odot}$. A scientific debate initiated concerning the identification of the low mass component, as it falls into the neutron star - black hole mass gap. The understanding of the nature of GW190814 event will offer rich information concerning open issues, the speed of sound and the possible phase transition into other degrees of freedom. In the present work, we made an effort to probe the nuclear equation of state along with the GW190814 event. Firstly, we examine possible constraints on the nuclear equation of state inferred from the consideration that the low mass companion is a slow or rapidly rotating neutron star. In this case, the role of the upper bounds on the speed of sound is revealed, in connection with the dense nuclear matter properties. Secondly, we systematically study the tidal deformability of a possible high mass candidate existing as an individual star or as a component one in a binary neutron star system. As the tidal deformability and radius are quantities very sensitive on the neutron star equation of state, they are excellent counters on dense matter properties. We conjecture that similar isolated neutron stars or systems may exist in the Universe and their possible future observation will shed light on the maximum neutron star mass problem.