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The thermal—viscous disk instability model in the AGN context

Published online by Cambridge University Press:  01 August 2006

Jean-Marie Hameury
Affiliation:
Observatoire de Strasbourg, CNRS/Université Louis Pasteur, 11 rue de l'Université, 67000 Strasbourg, France email: hameury@astro.u-strasbg.fr; viallet@astro.u-strasbg.fr
Jean-Pierre Lasota
Affiliation:
Institut d'Astrophysique de Paris, CNRS/Université Pierre et Maris Curie, 98bis Bd. Arago, 75015 Paris, France
Maxime Viallet
Affiliation:
Observatoire de Strasbourg, CNRS/Université Louis Pasteur, 11 rue de l'Université, 67000 Strasbourg, France email: hameury@astro.u-strasbg.fr; viallet@astro.u-strasbg.fr
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Abstract

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Accretion disks in AGN should be subject to the same disk instability responsible for dwarf novae outbursts and soft X-ray transients in cataclysmic variables (CVs) and LMXBs. It has been suggested that this thermal/viscous instability can account for long term variability of AGNs. We analyze here the application of the DIM to the AGN case, using our adaptive grid numerical code developed in the context of CVs, enabling us to fully resolve the disk radial structure. We show that in AGNs, the width of heating and cooling fronts is so small that they cannot be resolved by standard codes, and that they propagate on time scales much shorter than the viscous time. As a result, transition fronts propagate back and forth in the disk, leading only to small luminosity variations. Truncation of the inner part of the disk by e.g. an ADAF will not alter this result, but enables the presence of quiescent states.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2007

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