A variable-density absorption event in NGC 3227 mapped withSuzakuandSwift

Abstract

Context. The morphology of the circumnuclear gas accreting onto supermassive black holes in Seyfert galaxies remains a topic of much debate. As the innermost regions of active galactic nuclei (AGN) are spatially unresolved, X-ray spectroscopy, and in particular line-of-sight absorption variability, is a key diagnostic to map out the distribution of gas. Aims. Observations of variable X-ray absorption in multiple Seyferts and over a wide range of timescales indicate the presence of clumps/clouds of gas within the circumnuclear material. Eclipse events by clumps transiting the line of sight allow us to explore the properties of the clumps over a wide range of radial distances from the optical/UV broad line region (BLR) to beyond the dust sublimation radius. Time-resolved absorption events have been extremely rare so far, but suggest a range of density profiles across Seyferts. We resolve a weeks-long absorption event in the Seyfert NGC 3227. Methods. We examine six Suzaku and 12 Swift observations from a 2008 campaign spanning five weeks. We use a model accounting for the complex spectral interplay of three absorbers with different levels of ionization. We perform time-resolved spectroscopy to discern the absorption variability behavior. We also examine the IR to X-ray spectral energy distribution (SED) to test for reddening by dust. Results. The 2008 absorption event is due to moderately-ionized (log ξ ∼ 1.2-1.4) gas covering 90% of the line of sight. We resolve the density profile to be highly irregular, in contrast to a previous symmetric and centrally-peaked event mapped with RXTE in the same object. The UV data do not show significant reddening, suggesting that the cloud is dust-free. Conclusions. The 2008 campaign has revealed a transit by a filamentary, moderately-ionized cloud of variable density that is likely located in the BLR, and possibly part of a disk wind.

Suzaku Observations of Moderately Obscured (Compton-Thin) Active Galactic Nuclei Selected by Swift/Bat Hard X-Ray Survey

“…Radio-loud objects (e.g., PKS, 3C, or 4C sources) or blazar-type objects, which possibly possess jets, are not included because of possible contamination of the X-ray emission due to the presence of a jet. Also, we exclude three bright objects with complex spectra-NGC 3227, NGC 3516, and NGC 4151-which have been intensively analyzed with different models such as relativistic reflection components from the inner disk, complex absorbers, and multiple powerlaw components (e.g., Patrick et al 2012;Noda et al 2014;Beuchert et al 2015;Keck et al 2015).…”

A rapid occultation event in NGC 3227

“…Lamer et al 2003) and absorbed low X-ray states in previous X-ray observations (Rivers et al 2011;Markowitz et al 2009Markowitz et al , 2014. A study using XMM, Suzaku and Swift data (Beuchert et al 2015) found an outflowing warm absorber that is complex, with signatures from three zones of ionized gas with transit by one inhomogeneous clump of gas linking part of the absorber complex to the location of the optical broad-line region. Further to this, variations have been observed in the Fe K-shell absorption lines (Gofford et al 2013) and a so-called negative lag detected in the lag-frequency spectrum, indicating the presence of a significant reveberated signal from reprocessing gas out of the line-of-sight (De Marco et al 2013).…”

“…Time-resolved absorption events, such as that reported by (Beuchert et al 2015), are still quite rare. The observation of such in NGC 3227, along with its wide range of observed spectral states motivated the 2016 XMM/NuSTAR campaign comprising ∼320 ks of XMM-Newton time overlapping ∼ 160 ks of NuSTAR observations.…”

Nuclear molecular outflow in the Seyfert galaxy NGC 3227

“…. Recently, Beuchert et al (2015) derived column densities for the ionized absorbers of N H ∼ 5 − 16 × 10 22 cm −2 . They also discussed that the absorbers could be part of an overall clumpy medium located in the outermost dust free broad line region or the inner part of the dusty torus.…”