Timing behavior in the hard state of Cyg X-1. The time lag and coherence are calculated between the 2–4 keV and 0.5–1 keV bands. To guide the eye, the gray shaded region roughly indicates the frequency range of the feature, as indicated by the reduced coherence. (a) Observation 2636010101 (Γ ∼ 1.8) shows the clearest signature of the timing feature in the NICER data. A localized ∼30 ms hard lag at ∼1.6 Hz is present at the overlap region of the L₁ and L₂ components. The amplitude of L₂ is reduced at soft energies. The coherence drops at the peak frequency of the timing feature’s time lag, and appears asymmetric with respect to the time lag. (b) Observation 4690010107 is slightly harder at Γ ∼ 1.7 and shows coherent hard lags at low frequencies. At 0.5 Hz, a coherence drop indicates the presence of the timing feature. The time lag shows a shelf-like structure at this frequency with an amplitude around 30 ms (note that the y-axis is different). (c) Observation 0100320106 is affected by dipping and shows long soft lags at low frequencies at an overall reduced coherence. The timing feature is blended into the lag spectrum with similar amplitude as in the other observations.