The Morphology of the Outflow in the Grazing Envelope Evolution

Sagiv Shiber

doi:10.3390/galaxies6030096

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.

Highlights

Numerical simulations of the common envelope evolution (CEE) have been performed throughout the last thirty years [1,2,3,4,5,6,7,8]
We examined the outflow morphology of the grazing envelope evolution (GEE) as a result of jets that a secondary star launches when it accretes mass from the envelope of a giant star
We conducted hydrodynamical simulations of two phases, the onset of the GEE, when the secondary star orbits the giant star in a circular Keplerian motion at the giant surface, namely, it grazes the envelope from outside, and the spiralling-in phase, when the secondary star grazes the envelope from inside as it spirals-in

Summary

Introduction

Numerical simulations of the common envelope evolution (CEE) have been performed throughout the last thirty years [1,2,3,4,5,6,7,8]. When the secondary star accretes mass through an accretion disk and launches jets that interact with the envelope of the giant star. This possibility was first discussed in [15,16] for a neutron star, and for other companions [17,18,19]. The accretion disk launches two opposite jets that remove envelope mass and cause the giant radius to shrink simultaneously with the orbital separation. More extended study the companion was set to spiral in to the envelope while it launches jets [28] These simulations included different opening angles and velocities of the jets.

Results

The Onset of the GEE

GEE with Spiralling-in Orbits

Discussion