Optical Variability of Quasars with 20-Year Photometric Light Curves

Abstract

We study the optical $gri$ photometric variability of a sample of 190 quasars within the SDSS Stripe 82 region that have long-term photometric coverage during $\sim 1998-2020$ with SDSS, PanSTARRS-1, the Dark Energy Survey, and dedicated follow-up monitoring with Blanco 4m/DECam. With on average $\sim 200$ nightly epochs per quasar per filter band, we improve the parameter constraints from a Damped Random Walk (DRW) model fit to the light curves over previous studies with 10-15 yr baselines and $\lesssim 100$ epochs. We find that the average damping timescale ${\tau }_{\mathrm{DRW}}$ continues to rise with increased baseline, reaching a median value of $\sim 750$ days ($g$ band) in the rest-frame of these quasars using the 20-yr light curves. Some quasars may have gradual, long-term trends in their light curves, suggesting that either the DRW fit requires very long baselines to converge, or that the underlying variability is more complex than a single DRW process for these quasars. Using a subset of quasars with better-constrained ${\tau }_{\mathrm{DRW}}$ (less than 20\% of the baseline), we confirm a weak wavelength dependence of ${\tau }_{\mathrm{DRW}}\propto {\lambda }^{0.51\pm 0.20}$. We further quantify optical variability of these quasars over days to decades timescales using structure function (SF) and power spectrum density (PSD) analyses. The SF and PSD measurements qualitatively confirm the measured (hundreds of days) damping timescales from the DRW fits. However, the ensemble PSD is steeper than that of a DRW on timescales less than $\sim$ a month for these luminous quasars, and this second break point correlates with the longer DRW damping timescale.

arXiv comment20 pages, 24 figures

References in corpus (53)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• emcee: The MCMC Hammer
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• A Catalog of Quasar Properties from SDSS DR7
• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• Fast and scalable Gaussian process modeling with applications to astronomical time series
• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Active Galactic Nuclei: what's in a name?
• The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey
• Quantifying Quasar Variability As Part of a General Approach To Classifying Continuously Varying Sources
• Is Quasar Optical Variability a Damped Random Walk?
• A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging
• Long-term optical variability properties of the Palomar-Green quasars
• Flexible and Scalable Methods for Quantifying Stochastic Variability in the Era of Massive Time-Domain Astronomical Data Sets
• Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei
• The Dark Energy Survey Image Processing Pipeline
• The Sloan Digital Sky Survey Reverberation Mapping Project: Sample Characterization
• A characteristic optical variability timescale in astrophysical accretion disks
• Global Radiation Magneto-hydrodynamic Simulations of Sub-Eddington Accretion Disks around Supermassive Black Holes
• Structure Function Analysis of Long Term Quasar Variability
• Are the Variability Properties of the Kepler AGN Light Curves Consistent with a Damped Random Walk?
• Revisiting Stochastic Variability of AGNs with Structure Functions
• Variability in active galactic nuclei: confrontation of models with observations
• Quasar Optical Variability in the Palomar-QUEST Survey
• The Kepler Light Curves of AGN: A Detailed Analysis
• Optical variability of AGN in the PTF/iPTF survey
• Pan-STARRS1 variability of XMM-COSMOS AGN. II. Physical correlations and power spectrum analysis
• Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
• Accretion-induced variability links young stellar objects, white dwarfs, and black holes
• Dependence of the optical/UV variability on the emission line properties and Eddington ratio in active galactic nuclei
• Improving Damped Random Walk parameters for SDSS Stripe 82 Quasars with Pan-STARRS1
• Corona-Heated Accretion-disk Reprocessing (CHAR): A Physical Model to Decipher the Melody of AGN UV/optical Twinkling
• AGN Variability Analysis Handbook
• A Systematic Search for Periodically Varying Quasars in Pan-STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09
• The Discovery of Timescale-Dependent Color Variability of Quasars
• The QUEST-La Silla AGN variability survey: connection between AGN variability and black hole physical properties
• Extracting Information from AGN Variability
• Measuring Quasar Variability with Pan-STARRS1 and SDSS
• Variable Faint Optical Sources Discovered by Comparing POSS and SDSS Catalogs
• A Degeneracy in DRW Modelling of AGN Light Curves
• How far is quasar UV/optical variability from damped random walk at low frequency?
• Deep modeling of quasar variability
• The ensemble photometric variability of over $10^5$ quasars in the Dark Energy Camera Legacy Survey and the Sloan Digital Sky Survey
• Optically variable active galactic nuclei in the 3 yr VST survey of the COSMOS field
• Modeling Stochastic Variability in Multi-Band Time Series Data
• Correlation between Optical and UV Variability of Quasars
• Analyses on the Variability Asymmetry of Kepler AGNs
• Characterization of Optical Light Curves of Extreme Variability Quasars Over a ~16-yr Baseline
• Individual optical variability of Active Galactic Nuclei from the MEXSAS2 sample
• Observational nonstationarity of AGN variability: The only way to go is down!

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• The ensemble broad-frequency power spectrum of Stripe-82 quasars from multiple surveys
• VarIabiLity seLection of AstrophysIcal sources iN PTF (VILLAIN) I. Structure function fits to 71 million objects
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