We present an analysis of X-ray variability in a sample of 157 radio quiet quasars from the ROSAT archive, ranging from 0.1 <z <4.1. A maximum likelihood method is used to constrain the amplitude of variability in low signal to noise light curves. Through combining these light curves, we are able to identify trends with luminosity and redshift. The decline in variability amplitude with luminosity identified in local AGN (z <0.1) is seen to continue self-similarly out to high redshift. At redshifts greater than 2 there is evidence for an increase in QSO X-ray variability amplitude suggesting these quasars may contain smaller black holes than their local equivalents.
|Title of host publication||AGN Surveys, Proceedings of IAU Colloquium 184, ASP Conference Proceedings|
|Editors||R.F. Green, E. Ye. Khachikian, D.B. Sanders|
|Publisher||ASTRONOMICAL SOC PACIFIC|
|Publication status||Published - 2002|