First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN
By A. Markowitz, M. Krumpe, R. Nikutta. 2014
153 citations recorded by the source corpus.
We present an analysis of multi-timescale variability in line-of-sight X-ray absorbing gas as a function of optical classification in a large sample of Seyfert AGN to derive the first X-ray statistical constraints for clumpy-torus models. We systematically search for discrete absorption events in the vast archive of RXTE monitoring of dozens of nearby type I and Compton-thin type II AGN. We are sensitive to discrete absorption events due to clouds of full-covering, neutral or mildly ionized gas with columns >~ 10^(22-25) cm^-2 transiting the line of sight. We detect 12 eclipse events in 8 objects, roughly tripling the number previously published from this archive. Peak column densities span ~ 4-26 x 10^22 cm^-2. Event durations span hours to months. The column density profile for an eclipsing cloud in NGC 3783 is doubly spiked, possibly indicating a cloud that is being tidally sheared. We infer the clouds' distances from the black hole to span ~0.3 -140 x 10^4 R_g. In seven objects, the clouds' distances are commensurate with the outer portions of Broad Line Regions (BLR), or the inner regions of infrared-emitting dusty tori. We discuss implications for cloud distributions in the context of clumpy-torus models. The probability of observing a source undergoing an absorption event, independent of constant absorption due to non-clumpy material, is 0.006(+0.160,-0.003) for type Is and 0.110(+0.461,-0.071) for type IIs.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/482abbf171053424f9c519596648cb9dea0801aa
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Citations in the corpus
- New Spectral Model for Constraining Torus Covering Factors from Broadband X-Ray Spectra of Active Galactic Nuclei (2018, background): “…is a possible, if not likely, scenario in AGN is abundant from detailed spectroscopy (e.g., Arévalo et al. 2014, Baloković et al. 2014, Annuar et al. 2015) and studies of line-of-sight absorption variability (e.g., Risaliti et al. 2002, Torricelli-Ciamponi et al. 2014, Markowitz et al. 2014).”
- The dust covering factor in active galactic nuclei (2016, background): “Another indication of a presence of smooth, lowdensity inter-cloud medium comes from constant baseline level absorption, between the strong absorption events, in type 2 AGN wellmonitored with RXTE (Markowitz et al. 2014).”