Role of $\Delta$s in determining the properties of Neutron Stars in parameterized hydrostatic equilibrium

TL;DR

This study investigates how $\Delta$ resonances influence neutron star properties using a parameterized hydrostatic equilibrium model, resolving the $\Delta$ puzzle and aligning with recent gravitational wave and pulsar mass constraints.

Contribution

It introduces a parameterized hydrostatic equilibrium approach to account for $\Delta$ resonances in neutron stars, successfully explaining massive NS observations.

Findings

$\Delta$ resonances soften the EoS but still allow massive NSs.

The model satisfies constraints from GW170817 and pulsar mass measurements.

The $\Delta$ puzzle is resolved with modified pressure and self-gravity considerations.

Abstract

The possible existence of $\Delta$ resonances is inspected in the cold dense matter of neutron star (NS) core in presence of the hyperons. The diverse effects of variation in $\Delta$ mass on their formation and the equation of state (EoS) are studied in this work with an effective chiral model and the resultant NS properties are calculated with the help of parameterized Tolman-Oppenheimer-Volkoff equations (PTOV) to bring out the two important features of pressure in the context of massive NSs. The $\Delta$ puzzle is re-explored and resolved taking into account the concept of modified/parameterized inertial pressure and self-gravity in case of massive pulsars like PSR J1614-2230 and PSR J0348-0432. It is seen that although the presence of exotic matter like the hyperons and the $\Delta$s softens the EoS considerably, their presence in massive NSs can be successfully explained with the theory of parameterized hydrostatic equilibrium conditions. The results of this work also satisfy the constraints on $R_{1.4}$ and $R_{1.6}$ from the gravitational wave (GW170817) detection of binary NS merger. The constraint on baryonic mass from PSR J0737-3039 is also satisfied with the solutions of the PTOV equations for all the $\Delta$ masses considered.