Crust-core transition of a neutron star: effect of the temperature under strong magnetic fields

TL;DR

This study investigates how temperature and strong magnetic fields influence the crust-core transition in magnetars, revealing that magnetic effects persist at high fields and low temperatures, with implications for neutron star structure.

Contribution

It introduces a detailed analysis of temperature and magnetic field effects on the crust-core transition using relativistic mean-field models, highlighting the impact of symmetry energy slope variations.

Findings

Magnetic effects on crust-core transition diminish above 10^9 K for fields ≤ 5×10^16 G.

At higher magnetic fields (5×10^17 G), effects persist even above 10^9 K.

Multiple disconnected non-homogeneous matter regions can exist above the transition density.

Abstract

The effect of temperature on the crust-core transition of a magnetar is studied. The thermodynamical spinodals are used to calculate the transition region within a relativistic mean-field approach for the equation of state. Magnetic fields with intensities $5\times 10^{16}$ G and $5\times 10 ^{17}$ G are considered. It is shown that the effect on the extension of the crust-core transition is washed away for temperatures above $10^{9}$ K for magnetic field intensities $ \lesssim 5\times 10^{16}$ G but may still persist if a magnetic field as high as $5\times 10 ^{17}$G is considered. For temperatures below that value, the effect of the magnetic field on crust-core transition is noticeable and grows as the temperature decreases and, in particular, it is interesting to identify the existence of disconnected non-homogeneous matter above the $B=0$ crust core transition density. Models with different symmetry energy slopes at saturation show quite different behaviors. In particular, a model with a large slope, as suggested by the recent results of PREX-2, predicts the existence of up to four disconnected regions of non-homogeneous matter above the zero magnetic field crust-core transition density.