We investigate the hypothetical X17 boson on neutron stars and Quark Stars
(QSs) using various hadronic Equation of States (EoSs) with phenomenological or
microscopic origin. Our aim is to set realistic constraints on its coupling
constant and the mass scaling, with respect to causality and various possible
upper mass limits and the dimensionless tidal deformability Λ1.4​. In
particular, we pay special attention on two main phenomenological parameters of
the X17, the one is related to the coupling constant g that it has
with hadrons or quarks and the other with the in-medium effects through the
regulator C. Both are very crucial concerning the contribution on
the total energy density and pressure. In the case of considering the X17 as a
carrier of nuclear force in Relativistic Mean Field (RMF) theory, an admixture
into vector boson segment was constrained by 20\% and 30\%. In our
investigation, we came to the general conclusion that the effect of the
hypothetical X17 both on neutron and QSs constrained mainly by the causality
limit, which is a specific property of each EoS. Moreover, it depends on the
interplay between the main two parameters that is the interaction coupling
g and the in-medium effects regulator C. These effects
are more pronounced in the case of QSs concerning all the bulk properties.Comment: 12 pages, 14 figures, 2 table