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Signatures of X-ray reverberation in the power spectra of AGN

Signatures of X-ray reverberation in the power spectra of AGN
Signatures of X-ray reverberation in the power spectra of AGN
Aims: we study the effects of X-ray reprocessing in the power spectra (PSDs) of active galactic nuclei (AGNs).

Methods: we compute fully relativistic disc response functions in the case of lamp-post geometry using the full observed reflection spectrum for various X-ray source heights, disc inclination, and spin values of the central black hole. Since the observed PSD is equal to the product of the intrinsic power spectrum with the transfer function (i.e. the Fourier transform of the disc response function), we are able to predict the observed PSDs in the case of X-ray illumination of the inner disc.

Results: the observed PSD should show a prominent dip at high frequencies and an oscillatory behaviour with a decreasing amplitude at higher frequencies. The reverberation echo features should be more prominent in energy bands where the reflection component is more pronounced. The frequency of the dip is independent of energy, and it is mainly determined by the black hole mass and the X-ray source height. The amplitude of the dip increases with increasing black hole spin and inclination angle, as long as the height of the lamp is smaller than ~10 gravitational radii.

Conclusions: the detection of the X-ray reverberation signals in the PSDs can provide further evidence for X-ray illumination of the inner disc in AGN. Our results are largely independent of the assumed geometry of the disc-corona system, as long as it does not change with time, and the disc response function is characterized by a sharp rise, a plateau, and a decline at longer times. Irrespective of the geometry, the frequency of the main dip should decrease with increasing mean time of the response function, and the amplitude of the dip should increase with increasing reflection fraction
0004-6361
A13
Papadakis, I.
3c6b12c5-4229-42e5-8278-214b210d01b0
Pecháček, T.
d6c5ab02-f64c-44a4-be16-d81061743511
Dovčiak, M.
e3d584fc-50d8-41f4-b227-1bec1b5b400b
Epitropakis, A.
ba1b8bff-b304-4f31-883b-b8e3667e3d73
Emmanoulopoulos, Dimitrios
ee2db4c6-3379-4604-8711-f779fb74f538
Karas, V.
652ebd3f-247a-418c-861d-741e4eb88fa3
Papadakis, I.
3c6b12c5-4229-42e5-8278-214b210d01b0
Pecháček, T.
d6c5ab02-f64c-44a4-be16-d81061743511
Dovčiak, M.
e3d584fc-50d8-41f4-b227-1bec1b5b400b
Epitropakis, A.
ba1b8bff-b304-4f31-883b-b8e3667e3d73
Emmanoulopoulos, Dimitrios
ee2db4c6-3379-4604-8711-f779fb74f538
Karas, V.
652ebd3f-247a-418c-861d-741e4eb88fa3

Papadakis, I., Pecháček, T., Dovčiak, M., Epitropakis, A., Emmanoulopoulos, Dimitrios and Karas, V. (2016) Signatures of X-ray reverberation in the power spectra of AGN. Astronomy & Astrophysics, 588, A13. (doi:10.1051/0004-6361/201527246).

Record type: Article

Abstract

Aims: we study the effects of X-ray reprocessing in the power spectra (PSDs) of active galactic nuclei (AGNs).

Methods: we compute fully relativistic disc response functions in the case of lamp-post geometry using the full observed reflection spectrum for various X-ray source heights, disc inclination, and spin values of the central black hole. Since the observed PSD is equal to the product of the intrinsic power spectrum with the transfer function (i.e. the Fourier transform of the disc response function), we are able to predict the observed PSDs in the case of X-ray illumination of the inner disc.

Results: the observed PSD should show a prominent dip at high frequencies and an oscillatory behaviour with a decreasing amplitude at higher frequencies. The reverberation echo features should be more prominent in energy bands where the reflection component is more pronounced. The frequency of the dip is independent of energy, and it is mainly determined by the black hole mass and the X-ray source height. The amplitude of the dip increases with increasing black hole spin and inclination angle, as long as the height of the lamp is smaller than ~10 gravitational radii.

Conclusions: the detection of the X-ray reverberation signals in the PSDs can provide further evidence for X-ray illumination of the inner disc in AGN. Our results are largely independent of the assumed geometry of the disc-corona system, as long as it does not change with time, and the disc response function is characterized by a sharp rise, a plateau, and a decline at longer times. Irrespective of the geometry, the frequency of the main dip should decrease with increasing mean time of the response function, and the amplitude of the dip should increase with increasing reflection fraction

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Accepted/In Press date: 7 January 2016
e-pub ahead of print date: 3 October 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401489
URI: http://eprints.soton.ac.uk/id/eprint/401489
ISSN: 0004-6361
PURE UUID: 098cc264-09e7-4698-98cc-09c1d27219c6
ORCID for Dimitrios Emmanoulopoulos: ORCID iD orcid.org/0000-0002-3335-2446

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Date deposited: 17 Oct 2016 13:19
Last modified: 10 Dec 2019 01:41

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