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A search for X-ray reprocessing echoes in the power spectral density functions of AGN

A search for X-ray reprocessing echoes in the power spectral density functions of AGN
A search for X-ray reprocessing echoes in the power spectral density functions of AGN
We present the results of a detailed study of the X-ray power spectral density (PSD) functions of 12 X-ray bright AGN, using almost all the archival XMM–Newton data. The total net exposure of the EPIC-pn light curves is larger than 350 ks in all cases (and exceeds 1 Ms in the case of 1H 0707?497). In a physical scenario in which X-ray reflection occurs in the inner part of the accretion disc of AGN, the X-ray reflection component should be a filtered echo of the X-ray continuum signal and should be equal to the convolution of the primary emission with the response function of the disc. Our primary objective is to search for these reflection features in the 5–7 keV (iron line) and 0.5–1 keV (soft) bands, where the X-ray reflection fraction is expected to be dominant. We fit to the observed periodograms two models: a simple bending power-law model (BPL) and a BPL model convolved with the transfer function of the accretion disc assuming the lamp-post geometry and X-ray reflection from a homogeneous disc. We do not find any significant features in the best-fitting BPL model residuals either in individual PSDs in the iron band, soft and full band (0.3–10 keV) or in the average PSD residuals of the brightest and more variable sources (with similar black hole mass estimates). The typical amplitude of the soft and full-band residuals is around 3–5 per cent. It is possible that the expected general relativistic effects are not detected because they are intrinsically lower than the uncertainty of the current PSDs, even in the strong relativistic case in which X-ray reflection occurs on a disc around a fast rotating black hole having an X-ray source very close above it. However, we could place strong constrains to the X-ray reflection geometry with the current data sets if we knew in advance the intrinsic shape of the X-ray PSDs, particularly its high-frequency slope.
0035-8711
1642-1655
Emmanoulopoulos, D.
ee2db4c6-3379-4604-8711-f779fb74f538
Papadakis, I.E.
81a6785c-8f4d-49a3-9eac-23ee4c743563
Epitropakis, A.
ba1b8bff-b304-4f31-883b-b8e3667e3d73
Pecháček, T.
d6c5ab02-f64c-44a4-be16-d81061743511
Dovčiak, M.
e3d584fc-50d8-41f4-b227-1bec1b5b400b
Mchardy, I.M.
4f215137-9cc4-4a08-982e-772a0b24c17e
Emmanoulopoulos, D.
ee2db4c6-3379-4604-8711-f779fb74f538
Papadakis, I.E.
81a6785c-8f4d-49a3-9eac-23ee4c743563
Epitropakis, A.
ba1b8bff-b304-4f31-883b-b8e3667e3d73
Pecháček, T.
d6c5ab02-f64c-44a4-be16-d81061743511
Dovčiak, M.
e3d584fc-50d8-41f4-b227-1bec1b5b400b
Mchardy, I.M.
4f215137-9cc4-4a08-982e-772a0b24c17e

Emmanoulopoulos, D., Papadakis, I.E., Epitropakis, A., Pecháček, T., Dovčiak, M. and Mchardy, I.M. (2016) A search for X-ray reprocessing echoes in the power spectral density functions of AGN. Monthly Notices of the Royal Astronomical Society, 461 (2), 1642-1655. (doi:10.1093/mnras/stw1359).

Record type: Article

Abstract

We present the results of a detailed study of the X-ray power spectral density (PSD) functions of 12 X-ray bright AGN, using almost all the archival XMM–Newton data. The total net exposure of the EPIC-pn light curves is larger than 350 ks in all cases (and exceeds 1 Ms in the case of 1H 0707?497). In a physical scenario in which X-ray reflection occurs in the inner part of the accretion disc of AGN, the X-ray reflection component should be a filtered echo of the X-ray continuum signal and should be equal to the convolution of the primary emission with the response function of the disc. Our primary objective is to search for these reflection features in the 5–7 keV (iron line) and 0.5–1 keV (soft) bands, where the X-ray reflection fraction is expected to be dominant. We fit to the observed periodograms two models: a simple bending power-law model (BPL) and a BPL model convolved with the transfer function of the accretion disc assuming the lamp-post geometry and X-ray reflection from a homogeneous disc. We do not find any significant features in the best-fitting BPL model residuals either in individual PSDs in the iron band, soft and full band (0.3–10 keV) or in the average PSD residuals of the brightest and more variable sources (with similar black hole mass estimates). The typical amplitude of the soft and full-band residuals is around 3–5 per cent. It is possible that the expected general relativistic effects are not detected because they are intrinsically lower than the uncertainty of the current PSDs, even in the strong relativistic case in which X-ray reflection occurs on a disc around a fast rotating black hole having an X-ray source very close above it. However, we could place strong constrains to the X-ray reflection geometry with the current data sets if we knew in advance the intrinsic shape of the X-ray PSDs, particularly its high-frequency slope.

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More information

Accepted/In Press date: 2 June 2016
e-pub ahead of print date: 8 June 2016
Published date: 11 September 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401482
URI: http://eprints.soton.ac.uk/id/eprint/401482
ISSN: 0035-8711
PURE UUID: b0822c6e-f67e-493f-bbeb-5a097ef0bf3d
ORCID for D. Emmanoulopoulos: ORCID iD orcid.org/0000-0002-3335-2446

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Date deposited: 17 Oct 2016 15:36
Last modified: 26 Nov 2019 01:42

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