Distribution of the mass-accretion rate at the accretion radius (Eq. (22), left panel) and the mass-accretion rate at the event horizon of the BH (Eq. (32), right panel), during the BH+OB star phase. The three colours denote the contributions from different initial orbital period ranges. The coloured histograms are stacked on each other, and the sum of the ordinate values equals unity. The black hatching shows the contribution from the BH+OB star binaries where a Keplerian accretion disc can form.