2025/07/14 by Shao-Peng Tang, Tang, Shao-Peng, Yong-Jia Huang +3 · 2 citations
Physics and Astronomy · Earth and Planetary Sciences · #Pulsars and Gravitational Waves Research #Geophysics and Gravity Measurements #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.2507.10025
The possible occurrence of a first-order hadron-quark phase transition (FOPT) in neutron-star interiors remains an open question. Whether such a transition can be directly tested with improved observations is a key challenge. Here, we incorporate the latest constraints, especially a new NICER radius measurement for PSR J0614--3329, into a nonparametric Gaussian Process (GP) EOS framework that explicitly includes a first-order transition. We find a Bayes factor of B≈2.3 when comparing models with and without an explicit phase transition, marginally favoring its presence. At 68% credibility, the transition onset density n\rm PT is either below 2 ns (corresponding to masses \lesssim1 M_\odot, with density jump Δn∼0.5 ns) or, more prominently, above 4 ns (near the central density of the heaviest NS, with Δn∼3 ns), where ns represents the nuclear saturation density. In addition, by using symmetry-energy expansion at low densities (<1.1 ns), we infer a slope parameter L=40.2+19.3-14.3 MeV, in good agreement with nuclear-experiment values. Intriguingly, L correlates positively with the radius difference between 1.4 M_\odot and 2.0 M_\odot stars.