Top panel: histogram of the residuals between the logarithmic power spectrum of Fig. 3a and its local median, weighted with its local variance σ. Bottom panel: two-dimensional histogram of the same quantity at some frequency at the x-axis and its first harmonic at the y-axis. In addition, we indicate for all counts with χ₁ ≥ 5 and χ₀ ≥ 10 the corresponding frequency in Hertz and its multiple of the neutron star frequency, ν₀ = 0.1323 Hz. To generate the histograms, we used the power spectrum shown in Fig. 3a, i.e. σ = 5 × 10⁵.