Probing the Optical/UV Continuum Variability of Active Galactic Nuclei with the Damped Random Walk Model

Abstract

Optical/UV continuum variability over baselines of up to 20 yr is investigated using the damped random walk (DRW) model for 1214 active galactic nuclei (AGNs) compiled from Y. Shen et al. and C. J. Burke et al. Among these, 115 AGNs with reliable DRW fitting and unbiased DRW parameters (timescale τ₂₅₀₀ and amplitude σ₂₅₀₀ at the rest-frame 2500~Å) are used to examine the relations between the variability and the accretion properties. We found a significant correlation of τ₂₅₀₀ with black hole mass (M_BH) and dimensionless accretion rate (ℳ̇) of the form τ₂₅₀₀ ∝ M_BH^0.50±0.07 ℳ̇^0.27±0.04, while the dependence on the continuum luminosity at 5100~Å and redshift becomes insignificant after controlling for M_BH. τ₂₅₀₀ also correlate with the mass accretion rate (Ṁ) as τ₂₅₀₀ ∝ Ṁ^0.41±0.04, which is consistent with the thermal timescale expected from the standard thin-disk model within 3σ uncertainties; while the average value is consistent with the expectations of the model, the scatter in the relation can be due to differences in the viscosity parameter (α) or in disk temperature profiles. Assuming that \tauuv\ corresponds to the accretion disk thermal timescale, the disk-emitting radius at rest-frame 2500~Å (R₂₅₀₀) is found to correlate with M_BH as R₂₅₀₀ ∝ M_BH^0.53±0.05. Using the microlensing-based R₂₅₀₀−M_BH relation of C. W. Morgan et al., α is statistically estimated to be 0.04±0.01.

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BibTeX RIS

BibTeX

@misc{ning2026probing,
  title = {{Probing the Optical/UV Continuum Variability of Active Galactic Nuclei with the Damped Random Walk Model}},
  author = {Xiang-Wei Ning and Wen-Jie Hu and Zi-Han Yuan and Yi Tang and Yan-Song Ma and Yu-Meng Gua and Le-Yi Huang and Wei-Hao Bian},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.27806},
  eprint = {2610.27806},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.27806},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Probing the Optical/UV Continuum Variability of Active Galactic Nuclei with the Damped Random Walk Model
AU  - Xiang-Wei Ning
AU  - Wen-Jie Hu
AU  - Zi-Han Yuan
AU  - Yi Tang
AU  - Yan-Song Ma
AU  - Yu-Meng Gua
AU  - Le-Yi Huang
AU  - Wei-Hao Bian
PY  - 2026
DA  - 2026/10/20
PB  - arXiv
DO  - 10.48550/arxiv.2610.27806
UR  - https://arxiv.org/abs/2610.27806
AB  - Optical/UV continuum variability over baselines of up to 20 yr is investigated using the damped random walk (DRW) model for 1214 active galactic nuclei (AGNs) compiled from Y. Shen et al. and C. J. Burke et al. Among these, 115 AGNs with reliable DRW fitting and unbiased DRW parameters (timescale τ_2500 and amplitude σ_2500 at the rest-frame 2500~Å) are used to examine the relations between the variability and the accretion properties. We found a significant correlation of τ_2500 with black hole mass (M_BH) and dimensionless accretion rate (ℳ̇) of the form τ_2500 ∝ M_BH^0.50±0.07 ℳ̇^0.27±0.04, while the dependence on the continuum luminosity at 5100~Å and redshift becomes insignificant after controlling for M_BH. τ_2500 also correlate with the mass accretion rate (Ṁ) as τ_2500 ∝ Ṁ^0.41±0.04, which is consistent with the thermal timescale expected from the standard thin-disk model within 3σ uncertainties; while the average value is consistent with the expectations of the model, the scatter in the relation can be due to differences in the viscosity parameter (α) or in disk temperature profiles. Assuming that \tauuv\ corresponds to the accretion disk thermal timescale, the disk-emitting radius at rest-frame 2500~Å (R_2500) is found to correlate with M_BH as R_2500 ∝ M_BH^0.53±0.05. Using the microlensing-based R_2500−M_BH relation of C. W. Morgan et al., α is statistically estimated to be 0.04±0.01.
ER  -

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