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Cited by 700Astrophysical Phenomena and ObservationsGalaxies: Formation, Evolution, PhenomenaStellar, planetary, and galactic studies

MODELING THE TIME VARIABILITY OF SDSS STRIPE 82 QUASARS AS A DAMPED RANDOM WALK

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MacLeod, C. L., Ivezić, Ž., Kochanek, C. S., Kozłowski, S., Kelly, B., Bullock, E., Kimball, A., Sesar, B. +5 more·2010·The Astrophysical Journal
DOI 10.1088/0004-637x/721/2/1014
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Abstract

We model the time variability of ∼9000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk (DRW). Using 2.7 million photometric measurements collected over 10 yr, we confirm the results of Kelly et al. and Kozłowski et al. that this model can explain quasar light curves at an impressive fidelity level (0.01–0.02 mag). The DRW model provides a simple, fast (O( N ) for N data points), and powerful statistical description of quasar light curves by a characteristic timescale (τ) and an asymptotic rms variability on long timescales (SF ∞ ). We searched for correlations between these two variability parameters and physical parameters such as luminosity and black hole mass, and rest-frame wavelength. Our analysis shows SF ∞ to increase with decreasing luminosity and rest-frame wavelength as observed previously, and without a correlation with redshift. We find a correlation between SF ∞ and black hole mass with a power-law index of 0.18 ± 0.03, independent of the anti-correlation with luminosity. We find that τ increases with increasing wavelength with a power-law index of 0.17, remains nearly constant with redshift and luminosity, and increases with increasing black hole mass with a power-law index of 0.21 ± 0.07. The amplitude of variability is anti-correlated with the Eddington ratio, which suggests a scenario where optical fluctuations are tied to variations in the accretion rate. However, we find an additional dependence on luminosity and/or black hole mass that cannot be explained by the trend with Eddington ratio. The radio-loudest quasars have systematically larger variability amplitudes by about 30%, when corrected for the other observed trends, while the distribution of their characteristic timescale is indistinguishable from that of the full sample. We do not detect any statistically robust differences in the characteristic timescale and variability amplitude between the full sample and the small subsample of quasars detected by ROSAT . Our results provide a simple quantitative framework for generating mock quasar light curves, such as currently used in LSST image simulations.

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Crossref · 10.1088/0004-637x/721/2/1014

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  • LSST will enable studies of quasar variability using accurate multicolor light curves for a few million quasars, constraining accretion physics and nuclear environments.

    “A study of quasar variability using accurate, multicolor light curves for a few million quasars, leading to constraints on the accretion physics and nuclear environments”

    From LSST: From Science Drivers to Reference Design and Anticipated Data Products (2019) · cites this paper as MacLeod et al. 2010

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Authors
MacLeod, C. L., Ivezić, Ž., Kochanek, C. S., Kozłowski, S., Kelly, B., Bullock, E., Kimball, A., Sesar, B., Westman, D., Brooks, K., Gibson, R., Becker, A. C., & de Vries, W. H.
Affiliations
  • University of Washington (US)
  • The Ohio State University (US)
  • Center for Astrophysics Harvard & Smithsonian (US)
Corresponding author
MacLeod, C. L.
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2010-09-03
Volume
721
Issue
2
Pages
1014-1033
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1088/0004-637x/721/2/1014
OpenAlex
W1967715705
Cited by
700
References
69
Citations by year
2026: 57 · 2025: 80 · 2024: 53 · 2023: 44 · 2022: 53 · 2021: 48 · 2020: 53 · 2019: 47 · 2018: 45 · 2017: 33 · 2016: 44 · 2015: 36 · 2014: 29 · 2013: 27 · 2012: 27
FWCI
13.94
Type
journal article
Language
en
Open access
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
Keywords
quasar variability, damped random walk, quasar light curves, SDSS Stripe 82, characteristic time scales, variability amplitude, black hole mass, Eddington ratio, accretion rate, radio-loud quasars, luminosity

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