Raw RVs of τ Ceti in the frequency domain (blue line) and binned in frequency (red dots). The best fit to the data (red line), using the model presented in Eq. (1), is obtained considering two power laws to account for supergranulation and granulation (black continuous lines), a Lorentzian profile to account for stellar oscillations (dashed line), and a constant to include white instrumental noise (dotted line).