Evolution of a high (left) and low (right) metallicity star of initially 10.5 M_⊙ that is stripped due to binary interaction. Letters A to J mark evolutionary points discussed in Sect. 3. Top: evolutionary tracks on the Hertzsprung-Russell diagram. The color indicates the total mass of hydrogen present at a given moment. For comparison, we show lines of constant radii as well as the evolution of the alternate-metallicity model in gray. Middle: evolution of the stellar structure of the stars in mass coordinate (Kippenhahn diagrams), given as a function of time until core collapse (τ_cc). Convective and overshooting regions are marked with double- and single-hatched regions, respectively. Colors indicate zones dominated by nuclear burning (yellow) or neutrino cooling (purple) where ϵ = sign(ϵ_nuc−ϵ_ν)log₁₀(max(1.0,|ϵ_nuc−ϵ_ν|)/[erg g⁻¹ s⁻¹]). Here ϵ_nuc is the nuclear energy generation rate and ϵ_ν the neutrino energy. The black line indicates the location of the stellar surface. Bottom: luminosity produced by hydrogen-, helium- and metal-burning as a fraction of the total luminosity produced by nuclear reactions (upper) and stellar radius (lower) as a function of time until core-collapse.