A Bayesian inference of hybrid stars with large quark cores
by
Sala de Conferências
Departamento de Física FCTUC
Neutron stars (NSs) are interesting objects capable of reaching densities unattainable on Earth. The properties of matter under these conditions remain a mystery. Exotic matter, including quark matter, may be present in the NS core. In this work, we explore the possible compositions of NS cores, in particular, the possible existence of large quark cores. We use the Relativistic Mean Field (RMF) model with nonlinear terms for the hadron phase and the Nambu–Jona-Lasinio (NJL) model and Mean Field Theory of Quantum Chromodynamics (MFTQCD) for the quark phase. Through Bayesian inference, we obtain different sets of equations: four sets with hybrid equations (three using the NJL model and the other using the MFTQCD model), and one set with only the hadron phase. One of the NJL sets is determined to discuss the hadron phase prior. We impose nuclear matter properties, X-ray observational data from NICER, perturbative QCD (pQCD) calculations, and causality on all sets. One set of hybrid NJL equations of state (EOSs) was also constrained by adding the GW170817 detection. All sets can describe observational data and theoretical restrictions. The MFTQCD allows a phase transition at lower densities compared to the NJL models. The MFTQCD model indicates that NSs with 1.4 M⊙ have quark matter in their inner core. However, NJL models suggest that it is more probable that 1.4 M⊙ NSs do not have quark matter. Both the MFTQCD and NJL models agree that there is quark matter in 2 M⊙ NSs.
Paulo Silva, Marcos Gouveia