Core-corona decomposition of compact (neutron) stars compared to NICER data including XTE J1814-338

TL;DR

This paper introduces a core-corona decomposition method for neutron star models, comparing it to NICER data, including outliers like XTE J1814-338, by accounting for uncertainties in the equation of state and potential dark matter presence.

Contribution

It presents a novel approach to modeling neutron stars by separating core and corona, incorporating uncertainties in the EoS and dark matter effects, and compares results with observational data.

Findings

Successful modeling of neutron star masses and radii including outlier XTE J1814-338.

Demonstrates the impact of EoS uncertainties and dark matter on neutron star structure.

Provides a new framework for interpreting NICER observational data.

Abstract

A core-corona decomposition of compact (neutron) star models is compared to recent NICER data of masses and radii. It is in particular interesting to capture the outlier XTE~J1814-338. Instead of integrating the TOV equations from the center to surface, we follow here another pathway by accommodating all uncertainties of the equation(s) of state (EoS) at supra-nuclear density or/and an unknown dark matter admixture in a parameterization of the core by its radius $r_x$, the included mass $m_x$ and the pressure $p_x$ at $r_x$. The corona, which may be dubbed also envelope or halo or outer crust, is assumed to be of standard-model matter where the EoS is supposed to be faithfully known.