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Revealing the X-ray variability of AGN with principal component analysis

Parker, M. L. and Fabian, A. C. and Matt, G. and Koljonen, K. I. I. and Kara, E. and Alston, W. and Walton, D. J. and Marinucci, A. and Brenneman, L. and Risaliti, G. (2015) Revealing the X-ray variability of AGN with principal component analysis. Monthly Notices of the Royal Astronomical Society, 447 (1). pp. 72-96. ISSN 0035-8711.

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We analyse a sample of 26 active galactic nuclei (AGN) with deep XMM–Newton observations, using principal component analysis (PCA) to find model-independent spectra of the different variable components. In total, we identify at least 12 qualitatively different patterns of spectral variability, involving several different mechanisms, including five sources which show evidence of variable relativistic reflection (MCG–6-30-15, NGC 4051, 1H 0707−495, NGC 3516 and Mrk 766) and three which show evidence of varying partial covering neutral absorption (NGC 4395, NGC 1365 and NGC 4151). In over half of the sources studied, the variability is dominated by changes in a power-law continuum, both in terms of changes in flux and power-law index, which could be produced by propagating fluctuations within the corona. Simulations are used to find unique predictions for different physical models, and we then attempt to qualitatively match the results from the simulations to the behaviour observed in the real data. We are able to explain a large proportion of the variability in these sources using simple models of spectral variability, but more complex models may be needed for the remainder. We have begun the process of building up a library of different principal components, so that spectral variability in AGN can quickly be matched to physical processes. We show that PCA can be an extremely powerful tool for distinguishing different patterns of variability in AGN, and that it can be used effectively on the large amounts of high-quality archival data available from the current generation of X-ray telescopes. We will make our PCA code available upon request to the lead author.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemSupporting Information
Parker, M. L.0000-0002-8466-7317
Fabian, A. C.0000-0002-9378-4072
Matt, G.0000-0002-2152-0916
Kara, E.0000-0003-0172-0854
Alston, W.0000-0003-2658-6559
Walton, D. J.0000-0001-5819-3552
Additional Information:© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 November 13. Received 2014 November 13. In original form 2014 May 30. First published online December 12, 2014. MLP acknowledges financial support from the Science and Technology Facilities Council (STFC).
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Subject Keywords: galaxies: active galaxies: nuclei galaxies: Seyfert
Issue or Number:1
Record Number:CaltechAUTHORS:20150406-083553799
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Official Citation: M. L. Parker, A. C. Fabian, G. Matt, K. I. I. Koljonen, E. Kara, W. Alston, D. J. Walton, A. Marinucci, L. Brenneman, and G. Risaliti Revealing the X-ray variability of AGN with principal component analysis MNRAS (February 11, 2015) Vol. 447 72-96 doi:10.1093/mnras/stu2424 First published online December 12, 2014
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56366
Deposited By: Ruth Sustaita
Deposited On:06 Apr 2015 18:20
Last Modified:17 Dec 2019 21:52

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