Radio observations of LS I +61 303 taken from Taylor & Gregory (1982). (a) Light curve at 5 and 10.5 GHz. An interval for separate analysis is shaded in green. (b) Periodogram of the full light curve. The most powerful peak is consistent with the orbital period. The fit to the periodogram, however, requires the superposition of two Gaussians. (c) Periodogram of super-orbital interval Θ = 0.0 − 0.5 (green-shaded area in panel a). The one-peaked profile is shifted toward the middle of the positions of P₁ and P₂ and is fitted by a single Gaussian.