We analyse the spectral variability of MCG–06-30-15 with 600 ks of XMM-Newton data , including 300 ks of new data from the joint XMM-Newton and NuSTAR 2013 observational campaign .
We use principal component analysis to find high resolution , model independent spectra of the different variable components of the spectrum .
We find that over 99 per cent of the variability can be described by just three components , which are consistent with variations in the normalisation of the powerlaw continuum ( \sim 97 per cent ) , the photon index ( \sim 2 per cent ) , and the normalisation of a relativistically blurred reflection spectrum ( \sim 0.5 per cent ) .
We also find a fourth significant component but this is heavily diluted by noise , and we can attribute all the remaining spectral variability to noise . All three components are found to be variable on timescales from 20 ks down to 1 ks , which corresponds to a distance from the central black hole of less than 70 gravitational radii .
We compare these results with those derived from spectral fitting , and find them to be in very good agreement with our interpretation of the principal components . We conclude that the observed relatively weak variability in the reflected component of the spectrum of MCG–06-30-15 is due to the effects of light-bending close to the event horizon of the black hole , and demonstrate that principal component analysis is an effective tool for analysing spectral variability in this regime .