Torsional oscillations of nonbare strange stars

TL;DR

This paper models the torsional oscillations of nonbare strange stars with layered quark and nuclear matter, revealing potential crust-breaking events triggered by glitch energy transfer.

Contribution

It introduces a detailed layered model of strange stars with coupled crusts and analyzes their torsional oscillations, highlighting the impact of glitch energy on crust stability.

Findings

Crust may break if >10^{-4} of glitch energy excites torsional oscillations.

Crystalline color superconducting crust absorbs little glitch energy, leading to large oscillations.

Torsional oscillations could serve as observational signatures of strange star structure.

Abstract

Strange stars are one of the possible compact stellar objects that can be formed after a supernova collapse. We consider a model of strange star having an inner core in the color-flavor locked phase surmounted by a crystalline color superconducting layer. These two phases constitute the {\it quarksphere}, which we assume to be the largest and heaviest part of the strange star. The next layer consists of standard nuclear matter forming a ionic crust, hovering on the top of the quarksphere and prevented from falling by a strong dipolar electric field. The dipolar electric field arises because quark matter is confined in the quarksphere by the strong interaction, but electrons can leak outside forming a few hundreds Fermi thick electron layer separating the ionic crust from the underlying quark matter. The ionic matter and the crystalline color superconducting matter constitute two electromagnetically coupled crust layers. We study the torsional oscillations of these two layers. Remarkably, we find that if a fraction larger than $10^{-4}$ of the energy of a Vela-like glitch is conveyed to a torsional oscillation, the ionic crust will likely break. The reason is that the very rigid and heavy crystalline color superconducting crust layer will absorb only a small fraction of the glitch energy, leading to a large amplitude torsional oscillation of the ionic crust.