The nature of X-ray spectral variability in Seyfert galaxies

@article{Taylor2003TheNO,
  title={The nature of X-ray spectral variability in Seyfert galaxies},
  author={Richard D. Taylor and Phil Uttley and Ian M. McHardy},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2003},
  volume={342}
}
We use a model-independent technique to investigate the nature of the 2–15 keV X-ray spectral variability in four Seyfert galaxies and distinguish between spectral pivoting and the two-component model for spectral variability. Our analysis reveals conclusively that the softening of the X-ray continuum with increasing flux in MCG?6-30-15 and NGC 3516 is a result of summing two spectral components: a soft varying component (SVC) with spectral shape independent of flux and a hard constant… 

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