AR_final file_2018-19

0.01 2×10 −3 5×10 −3 Frequency x Power Power Spectra for January 2016 0.1 1 10 −2 0 2 4 6 χ 2 Frequency (Hz) -20 -10 0 10 20 30 40 50 60 70 4 8 16 32 64 Time-lag (ms) Energy (keV) Time-lag at 1 Hz Figure 14: The frequency times the power density spectrum of Cygnus X-1 for photons in the 4–80 keV energy band for the month of January 2016. The power density spectrum has been fitted with two Lorentzian components (left panel). The right panel shows the time-lag as a function of energy at 1 Hz for the same month. The time-lags are increasing with the increase in energy and have been fitted using the fluctuation propagation model. ( 81 )