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

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.