Exploring the impact of Δ-isobars on neutron star

We include the Delta-isobars in the equation of state (EOS) of the neutron star (NS) and study its effects with various parameter sets of the Relativistic mean field (RMF) model. We compare our results with the NS's constraints from the mass-radius measurement of PSR J0348+0432, PSR J1614-2230, PSR J0030+0451, PSR J0740+6620, PSR J0952-0607, PSR J1810+1714 and tidal deformability of GW170817. We calculate the mass-radius profile and tidal deformability of the NS using 21 parameter sets of the RMF model. Analyzing the result with various parameters, it is clear that only a few parameter sets can simultaneously satisfy the constraints of NICER (Neutron Star Interior Composition Explorer) and GW170817. The NLD parameter set satisfies all the constraints of NICER and GW170817. For its strong predictive power for the bulk properties of the neutron star, we take the NLD parameter set as a representative for the detailed calculation of the effect of Delta-isobar on the neutron star properties. We demonstrate that it is possible that Delta-isobar can produce at 2-3 times the saturation density by adjusting the coupling constants X-sigma Delta, X-rho Delta and X-omega Delta in an appropriate range. The bulk properties of the NS, such as the mass-radius profile and tidal deformability, are strongly affected by the interaction strength of Delta-isobar. Our calculation shows that it is also possible that by choosing X-sigma Delta, X-rho Delta and X-omega Delta to a suitable range, the threshold density of Delta-isobar becomes lower than the Lambda 0 hyperon. For a particular value of the Delta-coupling constants, R1.4 decreases by 1.7km. This paper gives an argumentative justification for allowing Delta-isobar degrees of freedom in the calculation of the NS properties.