A direct image of the obscuring disk surrounding an active galactic nucleus

Article Abstract:

Researchers have imaged the subarcsecond radiostructure of NGC1068, the archetype of active galactic nuclei (AGN), in order to test two predictions for very-long baseline interferometry (VLBI) observations. This involved using the 10-station Very Large Baseline Array (VLBA), boosted by the phased, 26-element Very Large Array (VLA). It was possible to produce the first direct image of a parsec-scale, ionized gas disk surrounding an AGN. It was inferred that the ionized gas disk traces the outer regions of the inner accretion disk.

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Quasi-periodic oscillations in X-ray emission from the Seyfert galaxy NGC5548

Article Abstract:

Seyfert galaxy NGC5548 emits X-rays in quasi-periodic oscillations (QPOs). Analysis of data obtained by the Exosat satellite shows that NGC5548 is the first object with an active galactic nuclei (AGN) known to produce X-ray QPOs. Similar findings from compact galaxy X-ray binaries indicate that QPOs result from material being absorbed within a dense object, probably a black hole. However, the low estimated mass for the black hole that may exist within NGC5548's AGN may be hard to reconcile with current theories of AGN structure.

Models, X-ray astronomy, Seyfert galaxies

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