Modelling the X-ray power spectra of AGN by using reprocessing echoes from an extended corona. (arXiv:1905.09559v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chainakun_P/0/1/0/all/0/1">Poemwai Chainakun</a>
Characteristic signatures that X-ray reverberation from an extended corona
can manifest in the observed PSD of AGN are investigated. The presence of two
X-ray blobs illuminating an accretion disc can cause the interference between
two reprocessing-echo components and produce distinct physical features in the
PSD. The oscillatory structures (e.g., dips and humps) are seen but, contrarily
to the lamp-post case, the strongest dip is not always the one at the lowest
frequency. Instead, we find the frequency where the strongest dip is seen
associates to the lower-source height while the lowest frequency where the
first dip appears links with the upper-source height. This is because the
reverberation timescales increase with the source height. Accurate modelling of
the PSD then helps put constraints to the lower and upper limit of the corona
extent. Furthermore, the reverberation signatures are less pronounced with
increasing number of sources that do not produce reflection (e.g., additional
X-rays from fast, relativistic outflows). The amplitude of the oscillations
also depends on the amount of dilution contributed by the X-ray sources, thus
encodes information about their relative brightness. Due to stronger dilutions,
robust detection of these signatures with the current observations will become
even more difficult if the corona is extended. Future observations made by
Athena will enable us to fit these characteristics in statistically significant
details, and to reveal the nature of the disc-corona system.
Characteristic signatures that X-ray reverberation from an extended corona
can manifest in the observed PSD of AGN are investigated. The presence of two
X-ray blobs illuminating an accretion disc can cause the interference between
two reprocessing-echo components and produce distinct physical features in the
PSD. The oscillatory structures (e.g., dips and humps) are seen but, contrarily
to the lamp-post case, the strongest dip is not always the one at the lowest
frequency. Instead, we find the frequency where the strongest dip is seen
associates to the lower-source height while the lowest frequency where the
first dip appears links with the upper-source height. This is because the
reverberation timescales increase with the source height. Accurate modelling of
the PSD then helps put constraints to the lower and upper limit of the corona
extent. Furthermore, the reverberation signatures are less pronounced with
increasing number of sources that do not produce reflection (e.g., additional
X-rays from fast, relativistic outflows). The amplitude of the oscillations
also depends on the amount of dilution contributed by the X-ray sources, thus
encodes information about their relative brightness. Due to stronger dilutions,
robust detection of these signatures with the current observations will become
even more difficult if the corona is extended. Future observations made by
Athena will enable us to fit these characteristics in statistically significant
details, and to reveal the nature of the disc-corona system.
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