The Physical Mechanism of Radio-quiet Turn-on Changing-look Active Galactic Nuclei

It is suggested that the variation of the mass accretion rate in the accretion disk may be responsible for the occurrence of most changing-look active galactic nuclei (CL AGNs). However, the viscous timescale of a thin disk is far longer than the observed timescale of CL AGNs. Though this problem ca...

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Veröffentlicht in:The Astrophysical journal Jg. 988; H. 2; S. 207 - 213
Hauptverfasser: Li, Shuang-Liang, Cao, Xinwu
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Philadelphia The American Astronomical Society 01.08.2025
IOP Publishing
Schlagworte:
Accretion
Accretion disks
Active galactic nuclei
Advection
Black hole physics
Magnetic fields
Time
ISSN:0004-637X, 1538-4357
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Zusammenfassung:It is suggested that the variation of the mass accretion rate in the accretion disk may be responsible for the occurrence of most changing-look active galactic nuclei (CL AGNs). However, the viscous timescale of a thin disk is far longer than the observed timescale of CL AGNs. Though this problem can be resolved by introducing the large-scale magnetic field, the mechanism for radio-quiet CL AGNs with a weak/absent large-scale magnetic field remains a mystery. In this work, we assume that the thin accretion disk is collapsed from the inner advection-dominated accretion flow (ADAF) instead of being formed from the outer thin disk through advection. This idea is tested by comparing the cooling timescale ( t cool ) of an ADAF with the observed timescale ( t tran ) of turn-on CL AGNs. We compile a sample of 102 turn-on CL AGNs from the archived data and calculate the cooling timescale of an ADAF with the critical mass accretion rate based on some conventional assumptions. It is found that t cool is much shorter than t tran in most of the CL AGNs, which validates our assumption, though t cool is not consistent with t tran ( t cool  <  t tran ). However, this is reasonable since most of the CL AGNs were observed only two times, indicating that the observed timescale t tran is the maximum value because the changing-look behavior can indeed happen before the second observation.
Bibliographie:Galaxies and Cosmology
AAS65671
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/adec76