Speaker
Description
We perform a model-agnostic Bayesian analysis of the neutron-star-matter equation of state (EoS), using known ab-initio constraints and astrophysical observations to limit possible EoS behaviors at intermediate densities. Permitting explicit first-order phase transitions allows us to systematically search for twin-star solutions, i.e. the existence of stars degenerate in mass but differing in radius.
We find that current observational constraints exclude all but two classes of twin stars. The first is characterized by a first-order transition occurring at a very low density, with the material properties of the system either staying largely intact or moving away from the conformal limit upon entering the second branch.
In the second, more interesting class, the discontinuity in the mass-radius curve can either result from a rapid crossover transition or from a first order phase transition at a higher density, with the EoS again moving away from conformal behavior.
Given the very low Bayes factor for both types of solutions, we conclude that the standard scenario of twin stars, where one of the mass-degenerate pair contains a core of deconfined quark matter, can be reliably ruled out.