AUTHOR=Kazanas Demosthenes 

TITLE=Active galactic nuclei: global perspective and time-domain implications

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2024.1401797

DOI=10.3389/fspas.2024.1401797

ISSN=2296-987X

ABSTRACT=<p>A view of the global structure of active galactic nuclei (AGN) is presented herein following the detection of blue-shifted warm absorber (WA) and ultrafast outflow (UFO) absorption features in their X-ray spectra. A straightforward interpretation of these features suggests the presence of magnetohydrodynamic winds off the underlying accretion disks spanning a wide range of a few to <inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>∼</mml:mo><mml:mn>1</mml:mn><mml:msup><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mn>6</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> Schwarzschild radii. UFOs are associated with wind segments closest to a black hole, with decreasing ionization absorber species associated with these wind segments at increasingly larger distances; eventually, the wind segments at the largest distances are sufficiently cool and dusty to be associated with the AGN tori, as suggested in the past. Furthermore, spectroscopic X-ray observations at a sufficient resolution allow estimates of the mass fluxes of these winds, showing that they increase with radius. As a consequence, the mass flux of the underlying accretion disk must decrease toward the accreting black hole, eventually reaching a value smaller than that needed to convert the flow into an X-ray hot advection-dominated accretion flow; it is suggested that this hot segment of the accretion flow is responsible for the observed AGN X-rays (and galactic X-ray binaries) in place of the <italic>ad hoc</italic> corona assumed thus far. This work indicates that the properties of this component that are reflected in its relative luminosity to the viscous disk O-UV component depend on the source luminosity in broad agreement with the observations.</p>