Journal Article

X-ray variability of the Seyfert 1 Markarian 335: power spectrum and time lags

P. Arévalo, I. M. McHardy and D. P. Summons

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 388, issue 1, pages 211-218
Published in print July 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI:
X-ray variability of the Seyfert 1 Markarian 335: power spectrum and time lags

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To investigate further the comparison between active galactic nuclei (AGN) and black hole X-ray binaries, we have studied the main X-ray variability properties of the Seyfert 1 galaxy Mrk 335. We put particular emphasis on the X-ray time lags, which is a potentially important diagnostic of physical models. From a 100 ks observation by XMM–Newton, we show that the power spectrum of this source is well fitted by a bending power-law model, and the bend time-scale Tb is precisely at the value predicted by the Tb versus Hβ linewidth relation of McHardy et al. Variations in different energy bands show time-scale-dependent time lags, where higher energy bands lag lower ones. The lag, τ, varies as a function of the Fourier frequency, f, of the variability component in the light curves as τ∝f−1 at low frequencies, but there is a sharp cut-off in the lags at a frequency close to the bend frequency in the power spectrum. Similar behaviour is seen in black hole X-ray binary systems. The length of the time lags increases continuously with energy separation, in an almost loglinear relation. We show that the lag spectra can be produced by fluctuations propagating through the accretion flow as long as the energy spectrum of the X-ray emitting region hardens towards the centre.

Keywords: galaxies: active

Journal Article.  6459 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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