The Meissner Effect and Vortex Expulsion in Color-Superconducting Quark stars, and its Role for Re-heating of Magnetars

TL;DR

This paper explores how vortex expulsion in color-superconducting quark stars can reheat the star, potentially explaining high-temperature phenomena observed in magnetars and linking different types of neutron stars.

Contribution

It demonstrates that vortex expulsion in quark stars can produce significant thermal energy, providing a new mechanism for star re-heating and explaining observed high-energy astrophysical phenomena.

Findings

Vortex expulsion leads to high-temperature re-heating of quark stars.

Re-heating mechanism can explain properties of SGRs, AXPs, and XDINs.

Estimated quark deconfinement density is about five times nuclear saturation.

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 at least partially 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 paper, 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. From observations, we find this density to be of the order of five times that of nuclear saturation.