Forced eccentricity e_f, as a function of the semimajor axes of the binary a_B and the planetesimal a, for all the orbital solutions of γ-Cephei with residuals within the 1σ confidence level of the best fit. Top and bottom frames assume two different values for m_A. Each value of a_B implies different values of both m_B and e_B, obtained from the families of orbital fits presented in Fig. 5. Values of a_B for each best fit are shown with horizontal dashed lines.