High mass accretion rates onto evolved stripped-envelope massive stars by jet-induced mass removal

TL;DR

This study demonstrates that jet-induced mass removal during high-rate accretion onto evolved stripped-envelope stars significantly reduces stellar expansion, supporting models of luminous red novae and similar transients.

Contribution

It introduces a novel jet-induced mass removal scenario in stellar evolution models, showing how it moderates expansion during high-rate accretion onto Wolf-Rayet stars.

Findings

Jet-induced mass removal decreases stellar expansion by 2-5 times.

High accretion rates allow stars to maintain deep potential wells.

Supports models of luminous red novae with high-rate accretion and jet activity.

Abstract

Simulating one-dimensional stellar evolution models with MESA, we show that removing the outer inflated envelope of a mass-accreting evolved stripped-envelope star, like a Wolf-Rayet (WR) star, substantially moderates the stellar expansion during accretion at high-mass accretion rates. We study the accretion onto a star via an accretion disk, which launches jets that remove the high-entropy outer layers of the inflated envelope. This is the `jetted mass removal accretion scenario.' By manually removing the entire hydrogen-rich envelope from a red supergiant, we build a hydrogen-deficient WR stellar model with a mass of 6.03Mo and a radius of 0.67Ro. We then accrete mass onto it at a high rate. We mimic the real process of simultaneous mass addition near the equatorial plane and jet-induced mass removal from the outer envelope by dividing the accretion period into hundreds of pulses: in the first half of each pulse, we add mass, and in the second, we remove a fraction of this mass. The removal of tens of percent from the added mass decreases the stellar expansion by a factor of ~2-5. Our results show that WR stars can maintain a deep potential well and not expand much while accreting mass at high rates. This allows the formation of an accretion disk and the liberation of large amounts of gravitational energy. Our results strengthen models of intermediate-luminosity optical transients, such as luminous red novae, in which a non-degenerate star accretes at high rates and launches jets that power the transient event.