Vortex Dynamics in Color-Superconducting Quark stars: The Re-heating of Magnetars

TL;DR

This paper explores how vortex dynamics in color-superconducting quark stars can lead to re-heating mechanisms that explain high-temperature observations of certain neutron star types, linking their evolution and internal properties.

Contribution

It introduces a model where vortex expulsion and magnetic reconnection in quark stars cause significant re-heating, providing explanations for observed high-energy phenomena in specific star classes.

Findings

Re-heating can reach temperatures observed in SGRs, AXPs, and XDINs.

Vortex expulsion influences magnetic field decay and spin-down rates.

Estimated quark deconfinement density is five times nuclear saturation density.

Abstract

Compact stars made of quark matter rather than confined hadronic matter, are expected to form a color superconductor. This superconductor ought to be threaded with rotational vortex lines within which the star's interior magnetic field is confined. The vortices (and thus magnetic flux) would be expelled from the star during stellar spin-down, leading to magnetic reconnection at the surface of the star and the prolific production of thermal energy. In this Letter, we show that this energy release can re-heat quark stars to exceptionally high temperatures, such as observed for Soft Gamma Repeaters (SGRs), Anomalous X-Ray pulsars (AXPs), and X-ray dim isolated neutron stars (XDINs). Moreover, our numerical investigations of the temperature evolution, spin-down rate, and magnetic field behavior of such superconducting quark stars suggest that SGRs, AXPs, and XDINs may be linked ancestrally. Finally, we discuss the possibility of a time delay before the star enters the color superconducting phase, which can be used to estimate the density at which quarks deconfine. We find this density to be five times that of nuclear saturation.