Is the coexistence of strange quark stars and hadronic stars favored by astrophysical data? A Bayesian analysis

Hadronic stars and strange quark stars could coexist within the so-called two-families scenario. In this respect, hadronic matter and strange quark matter correspond to two distinct equilibrium phases described by two different equations of state. We perform here the first detailed Bayesian analysis that makes use of astrophysical and laboratory data in order to constrain the equations of state adopted within the two-families scenario for hadronic and strange quark matter. In particular, in hadronic matter we consider the possible formation of hyperons and delta resonances (beside nucleons) within a class of non linear relativistic mean field models and in quark matter we consider the possible formation of a color-superconducting phase within a bag-like model. Results of the analysis indicate that, while at present both scenarios remain compatible with the data, the comparison of the Bayesian evidences shows a preference for the two-families scenario relative to our purely hadronic one-family baseline. Evaluating whether the data similarly favor the two-families scenario over a one-family model that includes hybrid stars is left to future work. The strength of this preference depends on the adopted dataset: it is moderate when only the most conservative astrophysical constraints are used, and becomes strong once the small-radius object PSR J0614–3329, the light and compact object HESS J1731–347, and the heavy-ion-collision flow data are included. Specifically, the two-families framework naturally relieves the tension between the intermediate-density softness of the equation of state required by small-radius objects, and the high-density stiffness needed to support massive pulsars. Ultimately, future detections of even more massive compact objects, very compact ordinary-mass objects, or precise measurements of two distinct masses with the same radius, would particularly strengthen the preference for two distinct compact-star families.