Detectability of binaries in the contiguous GBTDS fields, broken down by binary type. The number in parentheses indicates the fraction of the population that is shown in the figure; as there are many more star+star binaries than BH+star binaries, we only show a small fraction of the former for clarity. Gray points indicate sources with F146_Vega < 23.5 mag; red points indicate the subset of those which are astrometrically detectable (z_1s > 5). The positive correlation is due to Kepler’s third law as P_orb ∝ a^3/2, which is then modulated by scatter in δ_ql, ϖ, and σ_ast. Roman is most sensitive (i.e., large z_1s) to periods of 1 − 10 yr. The gap in the WD distribution is due to the choice made in population synthesis (Section 4.1).