IS QUASAR OPTICAL VARIABILITY A DAMPED RANDOM WALK?

By Y. Zu, C. Kochanek, S. Kozłowski, A. Udalski. 2012

187 citations recorded by the source corpus.

The damped random walk (DRW) model is increasingly used to model the variability in quasar optical light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar optical variability across all timescales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long timescales. We find good agreement with the DRW model on timescales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters, but this conclusion depends on the statistical test employed and is sensitive to whether the estimates of the photometric errors are correct to within ∼10%. On very short timescales (below a few months), we see some evidence of the existence of a cutoff below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. using quasar light curves from Kepler. On very long timescales (>a few years), the light curves do not constrain models well, but are consistent with the DRW model.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/aea70de10f9cda3fcd80fe74d8ab6dffbbd84759

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Citations in the corpus

A systematic search for close supermassive black hole binaries in the Catalina Real-time Transient Survey (2015, methodology): “…used as popular statistical descriptors of quasar optical variability, e.g., Kelly et al. (2009); MacLeod et al. (2012), there is a growing body of evidence that a more sophisticated approach is required (Mushotzky et al. 2011; Zu et al. 2013; Graham et al. 2014; Kasliwal, Vogeley & Richards 2015).”
STELLAR VELOCITY DISPERSION MEASUREMENTS IN HIGH-LUMINOSITY QUASAR HOSTS AND IMPLICATIONS FOR THE AGN BLACK HOLE MASS SCALE (2013, methodology): “The continuum is modeled as an autoregressive process using a damped random walk (DRW) model, which has shown to be a good statistical model of quasar variability (Gaskell & Peterson 1987; Kelly et al. 2009; Koz lowski et al. 2010; MacLeod et al. 2010; Zu et al. 2013).”
A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates (2016, methodology): “1 (Zu et al. 2013).”
THE MAN BEHIND THE CURTAIN: X-RAYS DRIVE THE UV THROUGH NIR VARIABILITY IN THE 2013 ACTIVE GALACTIC NUCLEUS OUTBURST IN NGC 2617 (2013, methodology): “…the continuum light curve using a damped ran om walk (DRW) model, which has been demonstrated to be a good statistical model of optical quasar variability using large (∼ 104) samples of quasar light curves (e.g., Kelly et al. 2009; Kozłowski et al. 2010; MacLeod et al. 2010; Zu et al. 2013b).”
The Sloan Digital Sky Survey Reverberation Mapping Project: Hα and Hβ Reverberation Measurements from First-year Spectroscopy and Photometry (2017, methodology): “We used the modeling code JAVELIN (Zu et al. 2011, 2013) as our primary time-series analysis method.”
False periodicities in quasar time-domain surveys (2016, background): “See Kelly, Bechtold & Siemiginowska (2009), MacLeod et al. (2010), Andrae et al. (2013) and Zu et al. (2013).”
THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: TECHNICAL OVERVIEW (2014, methodology): “…process) model to generate quasar continuum LCs (Kelly et al. 2009, 2014), which has been demonstrated to provide a reasonably good description of stochastic quasar continuum variability on the timescales of interest here (e.g., Kozłowski et al. 2010; MacLeod et al. 2010; Zu et al. 2013).”
REVERBERATION MEASUREMENTS OF THE INNER RADIUS OF THE DUST TORUS IN 17 SEYFERT GALAXIES (2014, background): “…UV-optical continuum emission, which has been demonstrated to be a good statistical model for AGN variability (e.g., Kelly et al. 2009; Koz lowski et al. 2010; MacLeod et al. 2010, 2012; Zu et al. 2013), and also assumes a top hat transfer function in the transfer equation of reverberation mapping.”
Modelling reverberation mapping data – II. Dynamical modelling of the Lick AGN Monitoring Project 2008 data set (2013, methodology): “…that we use is the same as a continuous-time first-order autoregressive process (CAR(1)), which has been found to be a good model for larger samples of AGN light curves (Kelly, Bechtold & Siemiginowska 2009; Kozłowski et al. 2010; MacLeod et al. 2010; Zu, Kochanek & Peterson 2011; Zu et al. 2013).”