Antikaons and higher order couplings in relativistic-mean field study of neutron stars

TL;DR

This study explores how higher order couplings and antikaon condensation affect neutron star properties, revealing their significant impact on the equation of state, composition, and mass-radius relation, and explaining recent observations.

Contribution

It introduces extended relativistic mean-field models incorporating higher order couplings and antikaons, providing new insights into neutron star structure and observable properties.

Findings

Antikaon condensation softens the equation of state.

Presence of antikaons makes the core more symmetric and lepton-deficient.

The observed 1.97 solar mass neutron star can be explained by different EoS scenarios.

Abstract

We investigate the role of higher order couplings, along with the condensation of antikaons ($K^-$ and $\bar K^0$), on the properties of neutron star (NS). We employ extended versions of the relativistic mean-field model, in which kaon-nucleon and nucleon-nucleon interactions are taken on the same footing. We find that the onset of condensation of $K^-$ and $\bar K^0$ highly depends not only on the strength of optical potential but also on the new couplings. The presence of antikaons leads to a softer equation of state and makes the neutron star core symmetric and lepton-deficient. We show that these effects strongly influence the mass-radius relation as well as the composition of neutron star. We also show that the recently observed 1.97$\pm$.04 solar mass NS can be explained in three ways: (i) a stiffer EoS with both antikaons, (ii) a relatively soft EoS with $K^-$ and (iii) a softer EoS without antikaons.