SHORT-TERM X-RAY VARIABILITY OF BLACK-HOLE CANDIDATES - GINGA RESULTS

The superposition technique is a new analysis method to obtain average properties of certain kinds of aperiodic time variations. Real averag e profiles of X-ray shots in Cyg X-l, GS 339-4, GS 2023+338 and GS 112 4-68 in the hard state are obtained in detail by applying the techniqu e to rapid time Variations of these sources observed by Ginga. The sho t profiles obtained are consistent with structures of power spectral d ensities and phase (time) lags below a few Hz. Soft energy spectra of the S-ray shots are thought to be the origin of soft excess components in time-averaged energy spectra. The shot profiles imply that the X-r ay shots arise from aperiodic mass accretion in the advection dominate d disk. These results are briefly described.