Triggering Eruptive Mass Ejection in Luminous Blue Variables

TL;DR

This paper investigates the mechanisms behind major eruptions in luminous blue variable stars, proposing that magnetic activity cycles or close companions can trigger runaway mass ejections, with implications for understanding stellar evolution and eruptions.

Contribution

It introduces a novel model suggesting magnetic energy release or companions trigger LBV eruptions, supported by stellar evolution simulations and magnetic field analysis.

Findings

Mass removal leads to star contraction and energy release.

Magnetic regions can trigger rapid mass ejection.

Eruptions are associated with magnetic activity or companions.

Abstract

We study the runaway mass loss process of major eruptions of luminous blue variables (LBVs) stars, such as the 1837-1856 Great Eruption of Eta Carinae. We follow the evolution of a massive star with a spherical stellar evolution numerical code. After the star exhausted most of the hydrogen in the core and had developed a large envelope, we remove mass at a rate of 1 Mo/year from the outer envelope for 20 years. We find that after removing a small amount of mass at a high rate, the star contracts and releases a huge amount of gravitational energy. We suggest that this energy can sustain the high mass loss rate. The triggering of this runaway mass loss process might be a close stellar companion or internal structural changes. We show that a strong magnetic field region can be built in the radiative zone above the convective core of the evolved massive star. When this magnetic energy is released it might trigger a fast removal of mass, and by that trigger an eruption. Namely, LBV major eruptions might be triggered by magnetic activity cycles. The prediction is that LBV stars that experience major eruptions should be found to have a close companion and/or have signatures of strong magnetic activity during or after the eruption.