Color-coded probability, p(ΔRV_sim > ΔRV_obs), that binary-induced motion would lead to a RV variation exceeding the observed ΔRV_obs in SMC AB9, for different combinations of orbital period, P_orb, and companion mass (see the main text for details). The higher this probability is, the less likely the source is an undetected binary. The dashed blue vertical line indicates P_orb = 1 yr.