Mass loss and magnetospheres of massive stars

TL;DR

This paper uses 2D numerical simulations to study how magnetic fields in massive OB and Wolf Rayet stars interact with their stellar winds, revealing complex magnetic confinement effects.

Contribution

It provides new insights into the magnetic wind interactions in massive stars using high-resolution MHD simulations with a range of confinement parameters.

Findings

Weak magnetic fields open up and become split monopoles.

Magnetic fields can trap outflowing gas in certain regions.

Interaction complexity increases with stronger magnetic confinement.

Abstract

About ten percent of all OB stars show strong, large-scale surface magnetic fields. The interaction of the magnetic field and the wind is believed to be the cause for the X-ray emission shown by these objects. We therefore run numerical simulations in two dimensions for a number the O-type stars and Wolf Rayet stars to study the interaction of the stellar magnetic fields of these stars with their winds. While weak, dipolar magnetic fields leave the wind largely unmodified and the field opens up and becomes a split monopole, the interaction between magnetic field and outflowing gas is more complex as the magnetic field remains closed in some regions and outflowing gas can be trapped. We use the Nirvana MHD code with adaptive mesh refinement to study this interaction with high numerical resolution to model cases with confinement parameters up to $10^4$.