Upper critical field and (non)-superconductivity of magnetars

TL;DR

This paper models magnetar interiors to determine the conditions under which proton superconductivity persists or is destroyed by strong magnetic fields, impacting their neutrino emission and superfluid behavior.

Contribution

It combines realistic neutron star models with microscopic pairing calculations to identify the magnetic field thresholds for proton superconductivity in magnetars.

Findings

Magnetars with interior fields 0.1-2 x 10^{16} G are partially superconducting.

Fields above 2 x 10^{16} G destroy proton superconductivity.

Superconductivity status influences neutrino emission and superfluid dynamics.

Abstract

We construct equilibrium models of compact stars using a realistic equation of state and obtain the density range occupied by the proton superconductor in strong $B$-fields. We do so by combining the density profiles of our models with microscopic calculations of proton pairing gaps and the critical unpairing field $H_{c2}$ above which the proton type-II superconductivity is destroyed. We find that magnetars with interior homogeneous field within the range $0.1 \le B_{16}\le 2$, where $B_{16} = B/10^{16}$ G, are partially superconducting, whereas those with $B_{16} > 2$ are void of superconductivity. We briefly discuss the neutrino emissivity and superfluid dynamics of magnetars in the light of their (non)-superconductivity.