A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2018

A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability

Résumé

We present the spectral/timing properties of the bare Seyfert galaxy Ark 120 through a deep ∼420 ks XMM-Newton campaign plus recent NuSTAR observations and a ∼6-month Swift monitoring campaign. We investigate the spectral decomposition through fractional rms, co-variance and difference spectra, finding the mid-to long-timescale (∼day-year) variability to be dominated by a relatively smooth, steep component, peaking in the soft X-ray band. Additionally, we find evidence for variable Fe K emission redward of the Fe Kα core on long timescales , consistent with previous findings. We detect a clearly defined power spectrum which we model with a power law with a slope of α ∼ 1.9. By extending the power spectrum to lower frequencies through the inclusion of Swift and Rossi X-ray Timing Explorer data, we find tentative evidence of a high-frequency break, consistent with existing scaling relations. We also explore frequency-dependent Fourier time lags, detecting a negative ('soft') lag for the first time in this source with the 0.3-1 keV band lagging behind the 1-4 keV band with a time delay, τ , of ∼900 s. Finally, we analyse the variability in the optical and ultraviolet (UV) bands using the Optical/UV Monitor onboard XMM-Newton and the Ultra-Violet/Optical Telescope onboard Swift and search for time-dependent correlations between the optical/UV/X-ray bands. We find tentative evidence for the U-band emission lagging behind the X-rays with a time delay of τ = 2.4 ± 1.8 d, which we discuss in the context of disc reprocessing.
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Dates et versions

hal-01984082 , version 1 (16-01-2019)

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A P Lobban, D. Porquet, J N Reeves, A. Markowitz, E Nardini, et al.. A deep X-ray view of the bare AGN Ark 120. III. X-ray timing analysis and multiwavelength variability. Monthly Notices of the Royal Astronomical Society, 2018, 474 (3), pp.3237-3258. ⟨10.1093/mnras/stx2889⟩. ⟨hal-01984082⟩
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