f_GW − log₁₀ℳ_c pf_GW − log₁₀ℳ_c parameter space. The shaded areas indicate the region of resolved PTs for a PTA timing baseline of 10 years. The grey areas correspond to an angular separation between the pulsar and the CGW source of 90°, and the blue areas correspond to 22.5°. The darker and lighter shades refer to a pulsar distance of 1 kpc and 4 kpc, respectively. The red symbols indicate the positions of two exemplary SMBHB candidates in this parameter space, with f_GW estimates and upper limits of log₁₀ℳ_c from electromagnetic models or PTA analyses (OJ287: Titarchuk et al. 2023; Komossa et al. 2023, 3C66B: Cardinal Tremblay et al. 2025).