Typical example of a 10-s-long light curve and the corresponding IMFs. (a) The original light curve. (b) The high-frequency noise, which is the summation of IMF c₁ to c₂. (c) Third component, c₃, corresponding to the LFQPO’s harmonic. (d) Fourth component, c₄, corresponding to the ∼4-Hz oscillation. (e) Fifth component, c₅, corresponding to the LFQPO’s sub-harmonic. (f) The low-frequency noise, which is the summation of IMF c₆ to the final residual. On the y axis, the units are 10³ counts s⁻¹.