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Published January 1, 2014 | Published + Submitted
Journal Article Open

Principal component analysis of MCG–06-30-15 with XMM–Newton

Abstract

We analyse the spectral variability of MCG–06-30-15 with 600 k s of XMM–Newton data, including 300 k s 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 normalization of the power-law continuum (∼97 per cent), the photon index (∼2 per cent) and the normalization of a relativistically blurred reflection spectrum (∼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 time-scales from 20 down to 1 k s, 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.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 October 7. Received 2013 September 12; in original form 2013 August 19. First published online: November 2, 2013. MLP would like to thank Dan Wilkins and Roderick Johnstone for help with numerous technical issues and J. Malzac for helpful discussion, and acknowledges financial support from the Science and Technology Facilities Council (STFC). AM acknowledges Fondazione Angelo Della Riccia for financial support. ACF thanks the Royal Society for support.

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Published - MNRAS-2014-Parker-721-9.pdf

Submitted - 1310.1945v2.pdf

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