Canonical Time Variations of X-Rays from Black Hole Candidates in the Low-Intensity State

The power spectrum density functions of X-rays and the phase lags of the time variations between different energy X-rays were investigated for several black-hole candidates (Cyg X - 1, GX 339 - 4, and GS 2023 + 338) in their low-intensity state, to determine whether these density functions were different for different X-ray sources and at different occasions for the same source. The results suggest that, in these black hole candidates in the low-intensity state, the X-ray production process and the dynamics of accreting matter behavior are the same except for the processes which correspond to the Fourier frequencies below about 0.2 Hz.