NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-20 T21:53:17 PDT
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For refcode 2014MNRAS.439.1403M:
Retrieve 55 NED objects in this reference.
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Copyright by Royal Astronomical Society. 2014MNRAS.439.1403M First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN Markowitz, A. G.; Krumpe, M.; Nikutta, R. Abstract. We present an analysis of multitime-scale variability in line-of-sight X-ray-absorbing gas as a function of optical classification in a large sample of Seyfert active galactic nuclei (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 Rossi X-ray Timing Explorer 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^, i.e. there are no full-covering Compton-thick events in our sample. 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 outside the BLR by factors up to ~10 (the inner regions of infrared-emitting dusty tori). We discuss implications for cloud distributions in the context of clumpy-torus models. Eight monitored type II AGN show X-ray absorption that is consistent with being constant over time-scales from 0.6 to 8.4 yr. This can either be explained by a homogeneous medium, or by X-ray-absorbing clouds that each have N_H_ << 10^22^ cm^-2^. 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. Key words: galaxies: active, galaxies: Seyfert, X-rays: galaxies
Retrieve 55 NED objects in this reference.
Please click here for ADS abstract

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