Abstract
The impact of the equation of state (EoS) crust-core matching procedure on neutron star (NS) properties is analyzed within a meta-modeling approach. Using a Taylor expansion to parametrize the core equation of state (EoS) and the SLy4 crust EoS, we create two distinct EoS datasets employing two matching procedures. Each EoS describes cold NS matter in a β equilibrium that is thermodynamically stable and causal. It is shown that the crust-core matching procedure affects not only the crust-core transition but also the nuclear matter parameter space of the core EoS, and thus the most probable nuclear matter properties. An uncertainty of as much as 5% (8%) on the determination of low mass NS radii (tidal deformability) is attributed to the complete matching procedure, including the effect on core EoS. By restricting the analysis, imposing that the same set of core EoS is retained in both matching procedures, the uncertainty on the NS radius drops to 3.5% and below 1.5% for 1.9M⊙. Moreover, under these conditions, the crust-core matching procedure has a strong impact on the Love number k2, of almost 20% for 1.0M⊙ stars and 7% for 1.9M⊙ stars, but it shows a very small impact on the tidal deformability Λ, below 1%.
Highlights
Neutron stars (NSs) are astrophysical objects made of cold super-dense neutron-rich nuclear matter
The sampling procedure is independently done for each matching procedure, i.e., we are not testing if a sampled equation of state (EoS) gives a valid matching within both procedures
We have generated two distinct EoS datasets employing two matching procedures used in the literature, where the matchings are done in the P(μ) and P(e) planes
Summary
Neutron stars (NSs) are astrophysical objects made of cold super-dense neutron-rich nuclear matter. In order to determine the constraints set by the gravitational waves GW170817 detected from the merging of two NS and other observations, several studies have been performed that apply a huge set of meta-model EoS [29,30,32,33,34,35] In these studies different approaches have been considered to glue the core EoS to the crust. The first method uses a Maxwell construction, i.e., the transition occurs at constant baryonic chemical potential μc , while the transition happens at a constant energy density, ec , in the second method This other method was the one applied in [28] to build politropic parameterizations of well known EoSs. An analysis of the matching effect on the consistency of the causal and thermodynamic properties of the EoS was performed in [26], and it was shown that the matching on the pressure-energy density plane is thermodynamically inconsistent.
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