X-ray variability analysis of a large series of XMM-Newton + NuSTAR observations of NGC 3227

Abstract

We present a series of X-ray variability results from a long XMM-Newton + NuSTAR campaign on the bright, variable AGN NGC 3227. We present an analysis of the lightcurves, showing that the source displays typically softer-when-brighter behaviour, although also undergoes significant spectral hardening during one observation which we interpret as due to an occultation event by a cloud of absorbing gas. We spectrally decompose the data and show that the bulk of the variability is continuum-driven and, through rms variability analysis, strongly enhanced in the soft band. We show that the source largely conforms to linear rms-flux behaviour and we compute X-ray power spectra, detecting moderate evidence for a bend in the power spectrum, consistent with existing scaling relations. Additionally, we compute X-ray Fourier time lags using both the XMM-Newton and - through maximum-likelihood methods - NuSTAR data, revealing a strong low-frequency hard lag and evidence for a soft lag at higher frequencies, which we discuss in terms of reverberation models.

Accepted for publication in MNRAS; 19 pages, 13 figures, 4 tables; minor typographical errors corrected and reference list updated

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Cited by in corpus (6)

• The flaring X-ray corona in the quasar PDS 456
• Transient obscuration event captured in NGC 3227. I. Continuum model for the broadband spectral energy distribution
• Continuum optical-UV and X-ray variability of AGN: current results and future challenges
• Transient obscuration event captured in NGC 3227 IV. Origin of the obscuring cloud variability
• NuSTAR spectral analysis of three Seyfert galaxies: NGC 3227, NGC 5548 and MR 2251$-$178
• Are Compton-thin AGNs Globally Compton Thin?