Dynamical Bar-Mode Instability in Differentially Rotating Magnetized Neutron Stars

TL;DR

This study uses high-resolution 3D simulations to explore how magnetic fields influence the dynamical bar-mode instability in differentially rotating neutron stars, revealing that magnetic effects are generally minor but can suppress instability in extreme cases.

Contribution

It introduces the first comprehensive numerical analysis of magnetic field effects on bar-mode instability in neutron stars using the Cosmos++ code.

Findings

Magnetic fields have limited impact on bar-mode growth in typical neutron star models.

Only in extreme magnetic field cases can the growth of the bar mode be suppressed.

Magnetic effects are generally negligible in realistic neutron star configurations.

Abstract

This paper presents a numerical study over a wide parameter space of the likelihood of the dynamical bar-mode instability in differentially rotating magnetized neutron stars. The innovative aspect of this study is the incorporation of magnetic fields in such a context, which have thus far been neglected in the purely hydrodynamical simulations available in the literature. The investigation uses the Cosmos++ code which allows us to perform three dimensional simulations on a cylindrical grid at high resolution. A sample of Newtonian magneto-hydrodynamical simulations starting from a set of models previously analyzed by other authors without magnetic fields has been performed, providing estimates of the effects of magnetic fields on the dynamical bar-mode deformation of rotating neutron stars. Overall, our results suggest that the effect of magnetic fields are not likely to be very significant in realistic configurations. Only in the most extreme cases are the magnetic fields able to suppress growth of the bar mode.