  Prompted by recent discoveries of log-normal distributions in gamma-ray/X-ray
temporal variabilities of gamma-ray bursts (GRBs) and blazars, we re-examine
the X-ray variability of Cygnus X-1 in the hard/low state using Ginga data in
1990. It was previously reported that the distributions of the time intervals
between X-ray shots (flares) deviated from the Poisson distributions at short
time intervals: the occurrence of shots tended to be suppressed for several
seconds before and/or after a shot event. Detailed analyses show that this
deviation is larger for shots with larger peaks, and that the time-interval
distributions for large shots approach log-normal distributions with a peak at
the interval of 7--8 s. Furthermore, we also show that the peak-intensity
distribution for the shots is consistent with the log-normal distribution,
though no typical peak intensity can be seen. This might indicate the presence
of a physical link connecting the physics of black hole accretion flow and that
of jet/GRB formation.
