Neutron stars with small radii -- the role of delta resonances

TL;DR

This paper explores how including delta resonances in a flavor SU(3) sigma model affects neutron star properties, showing that small adjustments in coupling constants can align models with recent observations of smaller neutron star radii.

Contribution

It introduces a modified equation of state with delta resonances that can explain recent neutron star measurements better than purely nucleonic models.

Findings

Including delta resonances allows modeling smaller neutron star radii.

Adjusting delta resonance coupling reproduces observed mass-radius data.

The model supports the presence of hyperons and delta resonances in neutron star matter.

Abstract

Recent neutron star observations suggest that the masses and radii of neutron stars may be smaller than previously considered, which would disfavor a purely nucleonic equation of state. In our model, we use a the flavor SU(3) sigma model that includes delta resonances and hyperons in the equation of state. We find that if the coupling of the delta resonances to the vector mesons is slightly smaller than that of the nucleons, we can reproduce both the measured mass-radius relationship and the extrapolated equation of state.