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Extensive X-ray variability studies of NGC 7314 using long XMM–Newton observations

Extensive X-ray variability studies of NGC 7314 using long XMM–Newton observations
Extensive X-ray variability studies of NGC 7314 using long XMM–Newton observations
We present a detailed X-ray variability study of the low-mass active galactic nuclei (AGN) NGC 7314 using the two newly obtained XMM–Newton observations (140 and 130 ks), together with two archival data sets of shorter duration (45 and 84 ks). The relationship between the X-ray variability characteristics and other physical source properties (such as the black hole mass) are still relatively poorly defined, especially for low-mass AGN. We perform a new, fully analytical, power spectral density (PSD) model analysis method, which will be described in detail in a forthcoming paper, that takes into consideration the spectral distortions, caused by red-noise leak. We find that the PSD in the 0.5–10 keV energy range, can be represented by a bending power law with a bend around 6.7 × 10?5 Hz, having a slope of 0.51 and 1.99 below and above the bend, respectively. Adding our bend time-scale estimate, to an already published ensemble of estimates from several AGN, supports the idea that the bend time-scale depends linearly only on the black hole mass and not on the bolometric luminosity. Moreover, we find that as the energy range increases, the PSD normalization increases and there is a hint that simultaneously the high-frequency slope becomes steeper. Finally, the X-ray time-lag spectrum of NGC 7314 shows some very weak signatures of relativistic reflection, and the energy resolved time-lag spectrum, for frequencies around 3 × 10?4 Hz, shows no signatures of X-ray reverberation. We show that the previous claim about ks time delays in this source, is simply an artefact induced by the minuscule number of points entering during the time-lag estimation in the low-frequency part of the time-lag spectrum (i.e. below 10?4 Hz).
0035-8711
2413-2431
Emmanoulopoulos, D.
ee2db4c6-3379-4604-8711-f779fb74f538
Mchardy, I.
4f215137-9cc4-4a08-982e-772a0b24c17e
Vaughan, S.
f8cf1168-b49a-4376-9d2c-c990a21e865e
Papadakis, I.E.
81a6785c-8f4d-49a3-9eac-23ee4c743563
Emmanoulopoulos, D.
ee2db4c6-3379-4604-8711-f779fb74f538
Mchardy, I.
4f215137-9cc4-4a08-982e-772a0b24c17e
Vaughan, S.
f8cf1168-b49a-4376-9d2c-c990a21e865e
Papadakis, I.E.
81a6785c-8f4d-49a3-9eac-23ee4c743563

Emmanoulopoulos, D., Mchardy, I., Vaughan, S. and Papadakis, I.E. (2016) Extensive X-ray variability studies of NGC 7314 using long XMM–Newton observations. Monthly Notices of the Royal Astronomical Society, 460 (3), 2413-2431. (doi:10.1093/mnras/stw1128).

Record type: Article

Abstract

We present a detailed X-ray variability study of the low-mass active galactic nuclei (AGN) NGC 7314 using the two newly obtained XMM–Newton observations (140 and 130 ks), together with two archival data sets of shorter duration (45 and 84 ks). The relationship between the X-ray variability characteristics and other physical source properties (such as the black hole mass) are still relatively poorly defined, especially for low-mass AGN. We perform a new, fully analytical, power spectral density (PSD) model analysis method, which will be described in detail in a forthcoming paper, that takes into consideration the spectral distortions, caused by red-noise leak. We find that the PSD in the 0.5–10 keV energy range, can be represented by a bending power law with a bend around 6.7 × 10?5 Hz, having a slope of 0.51 and 1.99 below and above the bend, respectively. Adding our bend time-scale estimate, to an already published ensemble of estimates from several AGN, supports the idea that the bend time-scale depends linearly only on the black hole mass and not on the bolometric luminosity. Moreover, we find that as the energy range increases, the PSD normalization increases and there is a hint that simultaneously the high-frequency slope becomes steeper. Finally, the X-ray time-lag spectrum of NGC 7314 shows some very weak signatures of relativistic reflection, and the energy resolved time-lag spectrum, for frequencies around 3 × 10?4 Hz, shows no signatures of X-ray reverberation. We show that the previous claim about ks time delays in this source, is simply an artefact induced by the minuscule number of points entering during the time-lag estimation in the low-frequency part of the time-lag spectrum (i.e. below 10?4 Hz).

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Accepted/In Press date: 10 May 2016
e-pub ahead of print date: 12 May 2016
Published date: 11 August 2016
Organisations: Astronomy Group

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Local EPrints ID: 401483
URI: http://eprints.soton.ac.uk/id/eprint/401483
ISSN: 0035-8711
PURE UUID: f96493ed-4b69-4e23-8a1c-2cfb9c23aa59
ORCID for D. Emmanoulopoulos: ORCID iD orcid.org/0000-0002-3335-2446

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Date deposited: 17 Oct 2016 15:57
Last modified: 19 Nov 2019 01:42

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Author: I. Mchardy
Author: S. Vaughan
Author: I.E. Papadakis

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