Universal Nuclear Equation of State Introducing the Hypothetical X17 Boson

Within the scope of the Symmetry journal special issue on: “The Nuclear Physics of Neutron Stars”, we complemented the nuclear equation of state (EoS) with a hypothetical 17 MeV boson and observed that only instances with an admixture of 30%–40% satisfy all of the constraints. The successful EoS resulted in a radius of around 13 km for a neutron star with mass MNS≈1.4M⊙ and in a maximum mass of around MNS≈2.5M⊙. The value of the radius is in agreement with the recent measurement by NICER. The maximum mass is also in agreement with the mass of the remnant of the gravitational wave event GW190814. Thus, it appears that these EoSs satisfy all of the existing experimental constraints and can be considered as universal nuclear equations of state.