Hybrid Star Properties with NJL and MFTQCD Model: A Bayesian Approach

The composition of the core of neutron stars is still under debate. One possibility is that because of the high densities reached in their cores, matter could be deconfined into quark matter. The possible existence of hybrid stars is investigated using microscopic models to describe the different phases of matter. Within these microscopic models we aim at calculating the properties of neutron stars and matter. We want to probe the influence of pQCD calculations and analyze the properties that identify a transition to deconfined matter. A Bayesian approach using a Markov Chain Monte Carlo sampling process is applied to generate 8 sets of equations of state. A Maxwell construction describes the deconfinement transition. For the hadronic phase, we consider a stiff and a soft EOS obtained from the Relativistic Mean Field model with non-linear meson terms. For the quark phase, we use two different models: the NJL model with multiquark interactions and the Mean Field Theory of QCD, similar to the MIT bag model with a vector term. The model parameters were determined by Bayesian inference imposing observations from NICER and the phase transition density range. We have also applied restrictions from the pQCD calculations. Hybrid stars are compatible with current observational data. The restrictions of pQCD reduce the value of the maximum mass. However, even when applying this restriction, the models were able to reach 2.1 to 2.3 solar masses. The conformal limit was not attained at the center of the most massive stars. The vector interactions are essential to describe hybrid stars with a mass above two solar masses. The multiquark interactions affect the limits of some quantities considered as indicators of the presence of a deconfined phase. It is possible to find a set of EOS, that predict that inside NS the renormalized matter trace anomaly is always positive.