Principal component analysis of the X-ray variability in NGC 7469
  We apply Principal Component Analysis (PCA) to study the variability of the X-ray continuum in the Seyfert 1 galaxy NGC 7469. The PCA technique is used to separate out linear components contributing to variability between multiple datasets; the technique is often used in analysis of optical spectra, but has rarely been applied to AGN X-ray spectroscopy. Running a PCA algorithm on 0.3-10 keV EPIC data from a 150 ks XMM-Newton observation of NGC 7469, we describe the spectral components extracted and evaluate the usefulness of the PCA technique for understanding the X-ray continuum in AGN. 
A. J. Blustin, S. V. Fuerst, G. Branduardi-Raymont, M. J. Page, E.   Behar, J. S. Kaastra