Lockman Hole AGN variability with XMM

We detected flux variability with a significance >=3{sigma} in ~50% of the objects, including 68+/-11% and 48+/-15% among our samples of type-1 and type-2 AGN. However we found that the fraction of sources with best quality light curves that exhibit flux variability on the time scales sampled by our data is >=80%, i.e the great majority of the AGN population may actually vary in flux on long time scales.

The mean relative intrinsic amplitude of flux variability was found to be ~0.15 although with a large dispersion in measured values, from ~0.1 to ~0.65. The flux variability properties of our samples of AGN (fraction of variable objects and amplitude of variability) do not significantly depend on the redshift or X-ray luminosity of the objects and seem to be similar for the two AGN types. Using a broad band X-ray colour we found that the fraction of sources showing spectral variability with a significance >=3{sigma} is ~40% i.e. less common than flux variability.