Universal relations for compact stars with heavy baryons

TL;DR

This paper investigates the universal relations among global properties of compact stars with heavy baryons, confirming their validity across various conditions and extending their applicability to rotating stars, with implications for understanding dense matter.

Contribution

It confirms and extends universal relations like I-Love-Q for stars with heavy baryons, including hyperons and Δ resonances, and explores their behavior in rotating and static configurations.

Findings

Universal I-Love-Q relations hold for stars with heavy baryons.

Relations between parameters persist in rotating and static stars with hyperons and Δ resonances.

Heavy baryons cause 'bumps' in radial profiles of global property integrands.

Abstract

A set of hadronic equations of state derived from covariant density functional theory and constrained by terrestrial experiments, and astrophysical observations, in particular by the NICER experiment inferences is used to explore the universal relations among the global properties of compact stars containing heavy baryons at high densities. We confirm the validity of universal $I$-Love-$Q$ relations connecting the moment of inertia $(I)$, the tidal deformability ($\Lambda$), and the spin-induced quadrupole moment ($Q$) for isolated non-rotating stars. We further confirm the validity of the $I$-$C$-$Q$ relations connecting the moment of inertia, compactness $(C)$, and quadrupole moment for uniformly and slowly rotating stars, and extend the validity of these relations to maximally rotating sequences. We then investigate the relations between integral parameters of maximally rotating and static compact stars. The universalities are shown to persist for equations of state and compositions containing hyperons and $\Delta$ degrees of freedom. When heavy baryons are included, however, the radial profiles of integrands in expressions of global properties exhibit ``bumps", which are not present in the case of nucleonic stars in which case the profiles are smooth. We determine the coefficients entering the universal relations in the case of hyperonic and $\Delta$-resonance containing stars.