A companion star launching jets in the wind acceleration zone of a giant star

TL;DR

This study uses 3D hydrodynamical simulations to show that jets launched by a companion star inside the wind acceleration zone of an AGB star can significantly enhance mass loss by ejecting gas that would otherwise fall back, affecting stellar evolution.

Contribution

It introduces the first detailed 3D simulation of jet interactions within the wind acceleration zone of a giant star, revealing their role in increasing mass loss.

Findings

Jets bend inside the wind acceleration zone and eject mass in a belt.

Jet-wind interactions induce instabilities that transfer energy to the wind.

Jets can enhance the mass loss rate from the giant star.

Abstract

By conducting three-dimensional (3D) hydrodynamical simulations we find that jets that a main sequence companion launches as it orbits inside the wind acceleration zone of an asymptotic giant branch (AGB) star can efficiently remove mass from that zone. We assume that during the intensive wind phase a large fraction of the gas in the acceleration zone does not reach the escape velocity. Therefore, in the numerical simulations we blow the wind with a velocity just below the escape velocity. We assume that a main sequence companion accretes mass from the slow wind via an accretion disk, and launches two opposite jets perpendicular to the equatorial plane. This novel flow interaction shows that by launching jets a companion outside a giant star, but close enough to be in the acceleration zone of a slow intensive wind, can enhance the mass loss rate from the giant by ejecting some gas that would otherwise fall back onto the giant star. The jets are bent inside the wind acceleration zone and eject mass in a belt on the two sides of the equatorial plane. The jet-wind interaction contains instabilities that mix shocked jets' gas with the wind, leading to energy transfer from the jets to the wind. As well, our new simulations add to the rich variety of jet-induced outflow morphologies from evolved stars.