What Magnetar Seismology can Teach us about the Magnetic Fields

TL;DR

This paper explores how magnetar seismology can reveal the strength and structure of magnetic fields in neutron stars by analyzing oscillation frequencies and their fine structures in observed spectra.

Contribution

It derives the effect of magnetic fields on neutron star oscillation frequencies and interprets observed spectral features as Zeeman splitting to estimate ultra-strong crustal magnetic fields.

Findings

Magnetic fields significantly affect neutron star oscillation frequencies.

Observed spectral fine structures can be explained by Zeeman splitting.

Estimated crustal magnetic field strength is around 10^{15} Gauss or higher.

Abstract

The effect of magnetic fields on the frequencies of toroidal oscillations of neutron stars is derived to lowest order. Interpreting the fine structure in the QPO power spectrum of magnetars following giant flares reported by Strohmayer and Watts (2006) to be "Zeeman splitting" of degenerate toroidal modes, we estimate a crustal magnetic field of order 10^{15} Gauss or more. We suggest that residual m, -m symmetry following such splitting might allow beating of individual frequency components that is slow enough to be observed.