First-order phase transitions in the cores of neutron stars

I explore various scenarios for the phase transition within neutron-star matter. I do so by generating large model-agnostic ensemble using Gaussian Processes, both with and without explicit inclusion of first-order phase transitions (PTs). The ensemble is conditioned with state-of-the-art astrophysical and theoretical inputs in a fully Bayesian approach. I study how the current data affect the posterior probability of the location and the strength of the first-order PT. I find that peak structure of the sound speed is stable against inclusion of PTs. Furthermore, while the current data cannot differentiate between a crossover and a first-order PT, it suggests an exceedingly low probability of the absence of either within the stable branch of neutron stars.