Energy dependence of the double-peak QPO properties in 1A 0535+262 on MJD 59171 and 59174. Top panels: rms amplitude as a function of energy. Bottom panels: Phase lags (Δϕ_QPO). The filled blue and open red triangles represent the HF and LF QPOs, respectively. The differences in both rms amplitude (∼4.5% on Day 5 and ∼6.6% on Day 8) and phase lag (∼0.9π rad) remain approximately constant across the 27–120 keV energy range.