QUASI-PERIODIC OSCILLATIONS IN THE SHOT-NOISE MODEL OF X-RAY SOURCES

It is shown that quasi-periodic oscillations (QPO) can naturally appear in the framework of the shot noise model under the assumption that individual shots are not completely independent. A weak ''interaction'' between shots can be expected in many physical models, when an instability is developing in the region having a stable external supply of energy. Indeed in order to keep energy release stable on large time scales, the appearance of strong shots should affect the amplitude (''amplitude'' interaction) and/or probability of occurrence (''probability'' interaction) of the subsequent shots. The influence on the shape of the power density spectra has been considered in the simplest cases of pure ''amplitude'' and ''probability'' interactions. As the by-product of our analysis an exact formula for the power density spectrum disturbances due to the detector ''dead time'' effect has been obtained. The results can be applied to the QPO of the X-ray flux from black hole candidates.