Evolution of the ratio of the circularisation radius R_disk to the radius of the innermost stable circular orbit R_ISCO during the BH+O phase as a function of the time since the formation of the BH for (β,  η,  γ_±) = (1,  1/3,  1). The black horizontal line shows the dividing line above which an accretion disk is expected. The colour coding in the legend identifies the 17 progenitor WR+O star systems that are expected to give rise to the BH+O binaries.