Parameters of rotating neutron stars with and without hyperons

TL;DR

This paper investigates how the presence of hyperons affects the global properties of rotating neutron stars, comparing models with and without hyperons against astrophysical observations, and providing approximate formulas for key stellar parameters.

Contribution

It offers a detailed comparison of neutron star properties with and without hyperons, including approximate formulas for maximum mass, compactness, and spin evolution, enhancing understanding of dense matter.

Findings

Hyperons influence maximum mass and compactness of neutron stars.

Models with hyperons can still match the 2 Msun observational constraint.

Approximate formulas for stellar parameters as functions of spin frequency are provided.

Abstract

The discovery of a 2 Msun neutron star provided a robust constraint for the theory of exotic dense matter, bringing into question the existence of strange baryons in the interiors of neutron stars. Although many theories fail to reproduce this observational result, several equations of state containing hyperons are consistent with it. We study global properties of stars using equations of state containing hyperons, and compare them to those without hyperons to find similarities, differences, and limits that can be compared with the astrophysical observations. Rotating, axisymmetric, and stationary stellar configurations in general relativity are obtained, and their global parameters are studied. Approximate formulae describing the behavior of the maximum and minimum stellar mass, compactness, surface redshifts, and moments of inertia as functions of spin frequency are provided. We also study the thin disk accretion and compare the spin-up evolution of stars with different moments of inertia.