Constraints on Pasta Structure of Neutron Stars from Oscillations in Giant Flares

TL;DR

This paper investigates how the presence of nuclear pasta in neutron star crusts affects shear mode frequencies, suggesting that oscillation observations can reveal crustal pasta structures and potentially explain observed flare frequencies.

Contribution

It demonstrates the sensitivity of shear mode frequencies to pasta phases and proposes using stellar oscillation data to probe neutron star crust structures.

Findings

Pasta phases lower shear mode frequencies.

Fundamental and overtone frequencies depend differently on pasta.

Crust shear modes can explain observed flare frequencies.

Abstract

We show that the shear modes in the neutron star crust are quite sensitive to the existence of nonuniform nuclear structures, so-called "pasta". Due to the existence of pasta phase, the frequencies of shear modes are reduced, where the dependence of fundamental frequency is different from that of overtones. Since the torsional shear frequencies depend strongly on the structure of pasta phase, through the observations of stellar oscillations, one can probe the pasta structure in the crust, although that is quite difficult via the other observations. Additionally, considering the effect of pasta phase, we show the possibility to explain the all observed frequencies in the SGR 1806-20 with using only crust torsional shear modes.