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A characteristic optical variability time scale in astrophysical accretion disks
Colin J Burke1,2, Yue Shen3,4, Omer Blaes5
1Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Science (New York, N.Y.)
|August 13, 2021
Summary
Researchers studied optical variability in 67 active galactic nuclei. They found a correlation between variability time scale and black hole mass, suggesting a common accretion disk process across various scales.
Area of Science:
- Astrophysics
- Black Hole Physics
- Accretion Disk Dynamics
Background:
- Active galactic nuclei (AGN) feature accretion disks around supermassive black holes.
- These disks emit ultraviolet and optical radiation, exhibiting stochastic variability due to accretion flow physics.
- Understanding variability time scales is crucial for probing accretion disk properties.
Purpose of the Study:
- To measure optical continuum variability in a sample of 67 active galactic nuclei.
- To identify the characteristic time scale where the variability power spectrum flattens.
- To investigate the relationship between this time scale and black hole mass.
Main Methods:
- Optical photometric monitoring of 67 active galactic nuclei.
- Analysis of light curves to determine variability power spectra.
- Calculation of the characteristic flattening time scale for each AGN.
Main Results:
- A significant correlation was found between the variability time scale and black hole mass across a wide range of supermassive black holes.
- The observed time scale aligns with theoretical predictions for the thermal time scale at the UV-emitting radius in standard accretion disk models.
- Accreting white dwarfs exhibit similar behavior, suggesting a unified accretion disk process.
Conclusions:
- The study establishes a robust correlation between accretion disk variability time scales and black hole mass in AGN.
- This finding supports standard accretion disk theory and suggests a universal mechanism governing accretion disk behavior.
- The results imply that accretion processes around compact objects, from white dwarfs to supermassive black holes, share fundamental similarities.
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