Precession of magnetars: dynamical evolutions and modulations on polarized electromagnetic waves

TL;DR

This paper models the precession dynamics of magnetars, analyzing how their deformation affects timing residuals and polarized electromagnetic signals, providing a framework for future observational searches.

Contribution

It introduces a comprehensive model of magnetar precession incorporating electromagnetic torques and predicts observable polarization modulations in X-ray and radio signals.

Findings

Timing residuals vary with neutron star geometry and torques.

Polarization modulations depend on surface emission and magnetic field configuration.

Model predictions can guide future observational searches for magnetar precession.

Abstract

Magnetars are conjectured to be highly magnetized neutron stars (NSs). Strong internal magnetic field and elasticity in the crust may deform the stars and lead to free precession. We study the precession dynamics of triaxially-deformed NSs incorporating the near-field and the far-field electromagnetic torques. We obtain timing residuals for different NS geometries and torques. We also investigate the polarized X-ray and radio signals from precessing magnetars. The modulations on the Stokes parameters are obtained for thermal X-rays emitted from the surface of magnetars. For radio signals, we apply the simple rotating vector model (RVM) to give the modulations on the position angle (PA) of the polarization. Our results are comprehensive, ready to be used to search for magnetar precession with timing data and polarizations of X-ray and radio emissions. Future observations of precessing magnetars will give us valuable information on the geometry and the strength of the strong magnetic fields, the emission geometry, as well as the equation of state (EoS) of NSs.