Radial pulsations, moment of inertia and tidal deformability of dark energy stars

TL;DR

This paper models dark energy stars with anisotropic pressure using Chaplygin-type EoS, analyzing their stability, moment of inertia, and tidal deformability, and explores their potential as gravitational wave sources like GW190814.

Contribution

It introduces a framework for constructing anisotropic dark energy stars and examines their stability and observable properties, linking them to recent gravitational wave detections.

Findings

Radial stability criterion remains valid for dark energy stars.

Anisotropy significantly affects tidal deformability and gravitational redshift.

Dark energy stars could potentially explain the secondary component of GW190814.

Abstract

We construct dark energy stars with Chaplygin-type equation of state (EoS) in the presence of anisotropic pressure within the framework of Einstein gravity. From the classification established by Iyer et al. [Class. Quantum Grav. 2, 219 (1985)], we discuss the possible existence of isotropic dark energy stars as compact objects. However, there is the possibility of constructing ultra-compact stars for sufficiently large anisotropies. We investigate the stellar stability against radial oscillations, and we also determine the moment of inertia and tidal deformability of these stars. We find that the usual static criterion for radial stability $dM/d\rho_c >0$ still holds for dark energy stars since the squared frequency of the fundamental pulsation mode vanishes at the critical central density corresponding to the maximum-mass configuration. The dependence of the tidal Love number on the anisotropy parameter $\alpha$ is also examined. We show that the surface gravitational redshift, moment of inertia and dimensionless tidal deformability undergo significant changes due to anisotropic pressure, primarily in the high-mass region. Furthermore, in light of the detection of gravitational waves GW190814, we explore the possibility of describing the secondary component of such event as a stable dark energy star in the presence of anisotropy.