Hadronic matter phases and their application to rapidly rotating neutron stars

TL;DR

This paper investigates the internal hadronic matter phases of neutron stars, their equations of state, and how these influence the stars' structure and rotation, comparing theoretical models with observational data.

Contribution

The study introduces new equations of state for high-density matter and applies them to rapidly rotating neutron stars, analyzing their consistency with observations.

Findings

One EOS aligns with observational data.

Another EOS is inconsistent with observations.

Identified a key relation between star radius and rotation rate.

Abstract

Neutron stars are commonly considered as astronomical objects having highdensity interiors and an inner core region in which various hadronic matter phases are expected. Several studies show that the inner structures affect macroscopic phenomena of the star. However, we know that the inner structures of the star strongly depend on the equation of state (EOS). The EOS of high-density matter is still not clear and several recent observations indicate restrictions to EOSs. Theoretical studies should elucidate EOSs at high density and/or high temperature. For instance, many theoretical studies have attempted to account for the rotation effect of rapidly rotating neutron stars (i.e., pulsars). Accordingly, we also apply our EOSs to rapidly rotating stars. Furthermore, neutron stars generate a strong magnetic field. Several recent studies indicate that this magnetic field exerts restrictions on the EOS. In this paper, we focus on the investigation of the inner structures and the application of our EOSs to rotating stars. We find that one of our EOSs is consistent with observations, and another is inconsistent. We also find an important relation between the radius and rotation.