A Two-zone Accretion Disk in the Changing-look Active Galactic Nucleus 1ES 1927+654: Physical Implications for Tidal Disruption Events and Super-Eddington Accretion

Ruancun Li, Luis C. Ho, Claudio Ricci, Benny Trakhtenbrot

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The properties of slim accretion disks, while crucial for our understanding of black hole growth, have yet to be studied extensively observationally. We analyze the multiepoch broadband spectral energy distribution of the changing-look active galactic nucleus 1ES 1927+654 to derive the properties of its complex, time-dependent accretion flow. The accretion rate decays as M ̇ ∝ t − 1.53 , consistent with the tidal disruption of a 1.1 M star. Three components contribute to the spectral energy distribution: a central overheated zone resembling a slim disk, an outer truncated thin disk, and a hot corona. Photon trapping in the slim disk triggered by the high initial M ̇ was characterized by a low radiation efficiency (3%), which later more than doubled (8%) after M ̇ dropped sufficiently low for the disk to transition to a geometrically thin state. The blackbody temperature profile T ∝ R −0.60 for the inner overheated zone matches the theoretical expectations of a slim disk, while the effective temperature profile of T ∝ R −0.69 for the outer zone is consistent with the predictions of a thin disk. Both profiles flatten toward the inner boundary of the disk as a result of Compton cooling in the corona. Our work presents compelling observational evidence for the existence of slim accretion disks and elucidates the key parameters governing their behavior, paving the way for further exploration in this area.

Original languageEnglish
Article number50
JournalAstrophysical Journal
Volume975
Issue number1
DOIs
StatePublished - 1 Nov 2024

Funding

FundersFunder number
China Manned Space Project
National Natural Science Foundation of China11991052, 12233001, 11721303, 12011540375
National Key Research and Development Program of ChinaCMS-CSST-2021-A06, CMS-CSST-2021-A04, 2022YFF0503401
Fondo Nacional de Desarrollo Científico y TecnológicoFB210003, 1230345

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