Disk corona interaction: Mechanism for the disk truncation and spectrum change in low-luminosity active galactic nuclei

Ronald E. Taam*, B. F. Liu, W. Yuan, E. Qiao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

The truncation of an optically thick, geometrically thin accretion disk is investigated in the context of low-luminosity AGNs (LLAGNs). We generalize the disk evaporation model used in the interpretative framework of black hole X-ray binaries by including the effect of a magnetic field in accretion disks surrounding supermassive black holes. The critical transition mass accretion rate for which the disk is truncated is found to be insensitive to magnetic effects, but its inclusion leads to a smaller truncation radius in comparison to a model without its consideration. That is, a thin viscous disk is truncated for LLAGNs at an Eddington ratio less than 0.03 for a standard viscosity parameter (α = 0.3). An increase of the viscosity parameter results in a higher critical transition mass accretion rate and a correspondingly smaller truncation distance, the latter accentuated by greater magnetic energy densities in the disk. Based on these results, the truncation radii inferred from spectral fits of LLAGNs published in the literature are consistent with the disk evaporation model. The infrared emission arising from the truncated geometrically thin accretion disks may be responsible for the red bump seen in such LLAGNs.

Original languageEnglish (US)
Article number65
JournalAstrophysical Journal
Volume759
Issue number1
DOIs
StatePublished - Nov 1 2012

Keywords

  • X-rays: galaxies
  • accretion, accretion disks
  • black hole physics
  • galaxies: active

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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