Short time-scale X-ray variability of Active Galactic Nuclei

Abstract In this work we investigated the short time-scale variability of NGC 4051 and NGC 4388. A quasi-steady QPO of 3922±17 sec was detected for NGC 4051. For NGC 4388, we investigated the rapid spectral variability with a new “Moving Fit” method for processing of the dynamic X-ray spectra.