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The nature of X-ray spectral variability in MCG-6-30-15

Kammoun, E. S. and Papadakis, I. E. (2017) The nature of X-ray spectral variability in MCG-6-30-15. Monthly Notices of the Royal Astronomical Society, 472 (3). pp. 3131-3146. ISSN 0035-8711. doi:10.1093/mnras/stx2181.

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The flux–flux plot (FFP) method can provide model-independent clues regarding the X-ray variability of active galactic nuclei. To use it properly, the bin size of the light curves should be as short as possible, provided the average counts in the light-curve bins are larger than ∼200. We apply the FFP method, performed in 2013, to the simultaneous XMM–Newton and NuSTAR observations of the Seyfert galaxy MCG–6-30-15, in the 0.3–40 keV range. The FFPs above ∼1.6 keV are well described by a straight line. This result rules out spectral slope variations and the hypothesis of absorption-driven variability. Our results are fully consistent with a power-law component varying in normalization only, with a spectral slope of ∼2, plus a variable, relativistic reflection arising from the inner accretion disc around a rotating black hole. We also detect spectral components that remain constant over ∼4.5 d (at least). At energies above ∼1.5 keV, the stable component is consistent with reflection from distant, neutral material. The constant component at low energies is consistent with a blackbody spectrum of kTBB ∼ 100 eV. The fluxes of these components are ∼10–20% of the average continuum flux (in the respective bands). They should always be included in the models that are used to fit the spectrum of the source. The FFPs below 1.6 keV are non-linear, which could be due to the variable warm absorber in this source.

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Additional Information:© 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 August 16. Received 2017 July 24; in original form 2017 June 20. Published: 24 August 2017. We thank the anonymous referee for useful comments. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA; XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This research has made use of the NuSTAR Data Analysis Software (NUSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA).
Subject Keywords:galaxies: active – galaxies: individual: MCG–6-30-15 – galaxies: nuclei – galaxies: Seyfert –X-rays: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20170908-094351605
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Official Citation:E. S. Kammoun, I. E. Papadakis; The nature of X-ray spectral variability in MCG–6-30-15, Monthly Notices of the Royal Astronomical Society, Volume 472, Issue 3, 11 December 2017, Pages 3131–3146,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81264
Deposited By: Joy Painter
Deposited On:08 Sep 2017 16:48
Last Modified:15 Nov 2021 19:42

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