Time evolution of the black hole spin for the rotation normalised with specific angular momentum at ISCO S = 1.0 (left) and S = 2.0 (right). Thick lines represent self-gravitating models and thin lines show the case where self-gravity is neglected. Various initial black hole spin values are shown, as labelled in the plots and marked by dark green for a₀ = 0.85, violet for a₀ = 0.6, magenta for a₀ = 0.5, and light green for a₀ = 0.83. Models are labelled in both panels with symbols referring to Table A.1.