Long-term simulation of MHD jet launching from an orbiting star-disk system

TL;DR

This study uses 3D MHD simulations to explore how binary star systems influence jet launching, revealing effects like disk warps, spiral arms, and jet precession, with implications for understanding astrophysical jet behavior.

Contribution

It presents the first long-term 3D MHD simulations of jet launching in binary systems considering time-dependent gravitational effects and various system configurations.

Findings

Binary systems induce non-axisymmetric disk and jet features.

Disk accretion rates increase due to spiral wave angular momentum transport.

Jet precession occurs at moderate inclinations, with a critical angle around 10-30 degrees.

Abstract

We present fully three-dimensional magnetohydrodynamic jet launching simulations of a jet source orbiting in a binary system. We consider a time-dependent binary gravitational potential, thus all tidal forces that are experienced in the non-inertial frame of the jet-launching primary. We investigate systems with different binary separation, different mass ratio, and different inclination between the disk plane and the orbital plane. The simulations run over a substantial fraction of the binary orbital period. All simulations show similar local and global non-axisymmetric effects such as local instabilities in the disk and the jet, or global features such as disk spiral arms and warps, or a global re-alignment of the inflow-outflow structure. The disk accretion rate is higher than for axisymmetric simulations, most probably due to the enhanced angular momentum transport by spiral waves. The disk outflow leaves the Roche lobe of the primary and becomes disturbed by tidal effects. While a disk-orbit inclination of $10\degr$ still allows for a persistent outflow, an inclination of $30\degr$ does not, suggesting a critical angle in between. For moderate inclination we find indication for jet precession such that the jet axis starts to follow a circular pattern with an opening cone of $\simeq 8\degr$. Simulations with different mass ratio indicate a change of time scales for the tidal forces to affect the disk-jet system. A large mass ratio (a massive secondary) leads to stronger spiral arms, a higher (average) accretion and a more pronounced jet-counter jet asymmetry.