Strangeness and $\Delta$ resonance in compact stars with relativistic-mean-field models

TL;DR

This paper investigates how strangeness and $\Delta$ resonances influence the properties of baryonic matter and compact stars using relativistic-mean-field models, highlighting the importance of $\Delta$ resonances in matching recent astrophysical observations.

Contribution

It introduces the inclusion of $\Delta$ resonances in RMF models for compact stars and assesses their impact on observational constraints, which is a novel approach.

Findings

Including $\Delta$ resonances is crucial for modeling compact stars.

Small $ ho$-$\Delta$ coupling is favored by recent mass measurements.

The models align with GW170817 tidal deformability constraints.

Abstract

We explore the effects of strangeness and $\Delta$ resonance in baryonic matter and compact stars within the relativistic-mean-field (RMF) models. The covariant density functional PKDD is adopted for $N$-$N$ interaction, parameters fixed based on finite hypernuclei and neutron stars are taken for the hyperon-meson couplings, and the universal baryon-meson coupling scheme is adopted for the $\Delta$-meson couplings. In light of the recent observations of GW170817 with the dimensionless combined tidal deformability $197 \leq \bar{\Lambda}\leq 720$, we find it is essential to include the $\Delta$ resonances in compact stars, and small $\Delta$-$\rho$ coupling $g_{\rho \Delta}$ is favored if the mass $2.27{}_{-0.15}^{+0.17}\ M_\odot$ of PSR J2215+5135 is confirmed.