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Title: DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

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 ({alpha} = 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.

Authors:
 [1]; ; ;  [2]
  1. Academia Sinica Institute of Astronomy and Astrophysics-TIARA, P.O. Box 23-141, Taipei 10617, Taiwan (China)
  2. National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China)
Publication Date:
OSTI Identifier:
22086444
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; ASTRONOMY; ASTROPHYSICS; BLACK HOLES; COMPARATIVE EVALUATIONS; COSMOLOGY; DISTANCE; EMISSION SPECTRA; ENERGY DENSITY; GALAXY NUCLEI; LUMINOSITY; MAGNETIC FIELDS; MASS; PHOTON EMISSION; VISCOSITY; X RADIATION; X-RAY GALAXIES

Citation Formats

Taam, Ronald E., Liu, B. F., Yuan, W., and Qiao, E., E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn. DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/1/65.
Taam, Ronald E., Liu, B. F., Yuan, W., & Qiao, E., E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn. DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI. United States. doi:10.1088/0004-637X/759/1/65.
Taam, Ronald E., Liu, B. F., Yuan, W., and Qiao, E., E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn. Thu . "DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI". United States. doi:10.1088/0004-637X/759/1/65.
@article{osti_22086444,
title = {DISK CORONA INTERACTION: MECHANISM FOR THE DISK TRUNCATION AND SPECTRUM CHANGE IN LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI},
author = {Taam, Ronald E. and Liu, B. F. and Yuan, W. and Qiao, E., E-mail: r-taam@northwestern.edu, E-mail: bfliu@nao.cas.cn},
abstractNote = {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 ({alpha} = 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.},
doi = {10.1088/0004-637X/759/1/65},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}