The Morphology of the Outflow in the Grazing Envelope Evolution

TL;DR

This study uses simulations to analyze the outflow morphology during grazing envelope evolution, revealing how jet angles influence outflow geometry and velocity distribution around giant stars.

Contribution

First detailed simulation-based analysis of outflow structures and velocities in grazing envelope evolution considering jet opening angles.

Findings

Narrow jets produce polar outflows with high velocity.

Outflows tend to concentrate around the orbital plane during spiraling-in.

High-velocity outflows are closer to the poles with narrower jets.

Abstract

We study the grazing envelope evolution (GEE), where a secondary star, which orbits the surface of a giant star, accretes mass from the giant envelope and launches jets. We conduct simulations of the GEE with different half-opening angles and velocities, and simulate the onset phase and the spiralling-in phase. We discuss the resulting envelope structure and the outflow geometry. We find in the simulations of the onset phase with narrow jets that a large fraction of the ejected mass outflows along the polar directions. The mass ejected at these directions has the fastest velocity and the highest angular momentum magnitude. In the simulations of the spiralling-in phase, a large fraction of the ejected mass concentrates around the orbital plane. According to our findings, the outflow with the highest velocity is closer to the poles as we launch narrower jets. The outflow has a toroidal shape accompanied by two faster rings, one ring at each side of the equatorial plane. The interaction of the jets with the giant envelope causes these outflow structures, as we do not include in our simulations the secondary star gravity and the envelope self-gravity.