XTE J1814-338: A potential hybrid star candidate

TL;DR

This paper explores hybrid star models with phase transitions to explain the unusually small radius of the XTE J1814-338 pulsar, suggesting that certain equations of state can reconcile observations with theoretical predictions.

Contribution

It constructs hybrid equations of state incorporating phase transitions to account for the properties of XTE J1814-338, a potential hybrid star candidate.

Findings

Hybrid EOS with strong phase transition can explain small radius and mass.

Stability depends on the stiffness of the low-density phase.

Configurations are stable under slow phase conversion despite soft hadronic EOS.

Abstract

A recent analysis on the properties of the XTE J1814-338 pulsar yielded a small radius value around ~ 7 km. Notably, this estimation is significantly lower compared to the currently inferred values for the radius of neutron stars (as they are derived from both theoretical calculations and corresponding observations). In this paper, we focus on the construction of hybrid equations of state (EOSs) for the possible reconciliation of the exotic XTE J1814-338 properties. Our analysis indicates that an equation of state involving a sufficiently strong phase transition could potentially lead to the explanation of the size and mass of such a compact object. By examining the sign of the $dM/dP_c$ slope, we found that stellar configurations compatible to XTE J1814-338 are only stable for a "stiff" low density phase. For a "soft" hadronic EOS selection the stability of the resulting configurations may not be satisfied in terms of the turning point criterion. However, a complementary analysis, for the radial oscillations of the aforementioned configurations, indicated their stability when a slow phase conversion is considered.