Quasi-universal relations for generalized Skyrme stars

TL;DR

This paper demonstrates that the I-Love-Q relations are universal across various Skyrme-based models and uses these relations with gravitational wave data to evaluate the most accurate Skyrme model for neutron star matter.

Contribution

It extends the universality of I-Love-Q relations to Skyrme models and analyzes additional quasi-universal relations with observational data.

Findings

I-Love-Q relations hold for multiple Skyrme EoS and Einstein-BPS-Skyrme solutions.

The relations are independent of the specific nuclear matter EoS.

Observational data helps identify the Skyrme model best fitting neutron star properties.

Abstract

First proposed in 2013 by Yagi and Yunes, the quasi-universal \emph{I-Love-Q relations} consist of a set of relations between the moment of inertia, the spin-induced quadrupole moment and the electric quadrupolar tidal deformability of neutron stars which are independent of the Equation of State (EoS) within an accuracy of $\sim1\%$. In this work, we show that these relations hold for different Skyrme-based nuclear matter EoS and also for the star-like solutions of different Einstein-BPS-Skyrme-models, some of which do not even present a barotropic equation of state. Further, other quasi-universal relations are analyzed, and together with recent GW observations, we use them to select the generalized Skyrme model that better reproduces observations. Our results reaffirm both the universality of the \emph{I-Love-Q} relations and the suitability of generalized Skyrme models to describe nuclear matter inside neutron stars.