Time resolved X-ray spectroscopy of Seyfert 1 galaxies

We have performed a detailed analysis of the "long-look" ASCA observation of NGC 4151. We present results of time-resolved spectroscopy of the broad iron line using conventional spectral modeling and by examing the RMS spectra. The data exhibit complex changes in the iron line shape which do not appear to be simply related to the continuum. We discuss our results in the context of data from other high S/N observations of Seyfert 1 galaxies, many of which appear to point to the general conclusion that the line intensity does not respond to the continuum. We point out that this does not necessarily eliminate the possibility of reverberation mapping of the disk/black hole system since there are at least two sources in which the broad Fe-K line does appear to respond to the continuum. We emphasize that the overall variability properties of the Fe-K line, in the small sample of sources which have sufficient S/N, are different for each galaxy and a larger sample, studied with XMM, is required to reveal any general trends.