Enabling high mass accretion rates onto massive main sequence stars by outer envelope mass removal

TL;DR

This study demonstrates that massive main sequence stars can sustain high mass accretion rates by removing outer envelope material via jets, preventing excessive expansion and enabling growth to higher masses.

Contribution

The paper introduces a novel one-dimensional simulation approach combining mass accretion and jet-driven mass removal to model high-rate stellar growth.

Findings

Stars can accrete up to 10% of their mass without significant expansion.

Jet-driven mass removal allows high accretion rates while maintaining stellar structure.

The model explains phenomena like luminous red novae and Eta Carinae's eruption.

Abstract

Using the one-dimensional numerical code MESA, we simulate mass accretion at very high rates onto massive main sequence stars, M=30, 60, 80 Mo, and find that these stars can accrete up to 10% of their mass without expanding much if we consider a simultaneous mass removal by jets. In this jetted-mass-removal accretion scenario, the accretion is through an accretion disk that launches jets. When the star expands due to rapid mass accretion, it engulfs the inner zones of the accretion disk and the jets it launches. We assume that these jets remove the outer layers of the envelope. We mimic this in the one-dimensional numerical code by alternating mass addition and mass removal parts. We add mass and energy, the accretion energy, to the outer layers of the envelope, leading to rapid stellar expansion. When the star expands by a few tens of percent, we stop mass addition and start mass removal until the star returns to its initial radius. We also show that the density of the accretion disk is larger than the density of the outer layers of the inflated envelope, allowing the disk to launch jets inside the outer inflated envelope layers. Our results show that main sequence stars can accrete mass at high rates while maintaining the deep potential well, as some models of eruptive systems require, e.g., some luminous red novae, the grazing envelope evolution, and the 1837-1856 Great Eruption of Eta Carinae.