Absolute value of the scalar product, |s_ℓ,₁|, of the first PC eigenvector and the hyperdiagonal unit vector as a function of the trial period. Left: PSR B0540-69, same data as in Fig. 9. Right: PSR B0833-45, same data as in Fig. 10. In both cases, the optimum period lies within the plateau region, or where the maximum, ~1 is achieved. The dashed vertical line corresponds to P_PCA, the optimum value found by the first PC eigenvalue (from Figs. 9 and 10). The same behavior is shown in the high signal-to-noise ratio case for PSR B0531+21 in Fig. 8. The total time and observation data are stated in Table 1. eported periods by only taking the maxima reach very similar values. The difference between the two periods is ∆P = 120ns.