Role of local anisotropy in hybrid stars

TL;DR

This paper explores how pressure anisotropies influence the structural properties of hybrid stars, showing that moderate anisotropies can satisfy observational constraints and extreme anisotropies may explain some exotic compact objects.

Contribution

It introduces a detailed analysis of pressure anisotropies using the Bower-Liang model and assesses their impact on hybrid star characteristics and observational constraints.

Findings

Anisotropies affect maximum mass, radius, and central density of hybrid stars.

Moderate anisotropies can satisfy standard astrophysical constraints.

Extreme anisotropies may explain black widow pulsars and GW190814 object.

Abstract

Using the Bower-Liang model, we discuss how pressure anisotropies affect the microscopic and macroscopic properties of hybrid stars. We find that anisotropies affect the maximum mass, central density, and radius of the canonical stars. Anisotropies also affect the minimum neutron star mass that presents quarks in their core, as well as the total amount of quarks for the maximally massive stars. We also confront our results with standard constraints, such as the radius and the tidal parameter of the canonical star, as well as the mass and radius of the PSR J0740+6620 pulsar. We observe that moderate values for anisotropies could fulfill these constraints simultaneously. On the other hand, within more extreme degrees of anisotropies, more speculative constraints such as black widow pulsars PSR J0952-0607 and the mass-gap object in the GW190814 event can be explained as hybrid stars. We also investigate the role of anisotropies in the neutron stars' moment of inertia.