2025ApJ...986..188M

Giant eruptions are episodic high-rate mass-loss events that massive stars experience in the late-stage of their evolution before exploding as a core-collapse supernova. If a giant eruption occurs in a binary system, the companion star can accrete part of the mass. We use numerical simulations to analyze how the companion responds to accretion and how its structure and evolution are altered. We run a grid of massive stars with masses from 20 M_⊙ to 60 M_⊙, and accretion rates from 10^–4 to 0.1 M_⊙ yr^–1, over a duration of 20 yr. For accretion rates ≲0.01 M_⊙ yr^–1, the star remains on the hotter side of the HR diagram with a minor increase in luminosity without expanding because the accretion timescale exceeds the thermal time scale by a larger factor. Mass loss through stellar winds leads to a minor drop in luminosity shortly after the accretion phase as the star enters the recovery phase. For ≳0.01 M_⊙ yr^–1, the companion star experiences a sudden increase in luminosity by about one order of magnitude, inflates, and cools. Under the accreted gas layer, the star retains its structure and continues to eject radiation-driven wind during the recovery phase, namely the time it takes to regain equilibrium. Eventually, the accreted material mixes with the inner layers of the star and the star continues to evolve as a more massive star.