1202.3783 (Ying Zu et al.)

Is Quasar Variability a Damped Random Walk?    [PDF]

Ying Zu, C. S. Kochanek, Szymon Kozłowski, Andrzej Udalski

The damped random walk (DRW) model is increasingly used to model the variability in quasar light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar variability across all time scales. 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 time scales. We find excellent agreement with the DRW model on time scales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters. On very short time scales (below a few months), we see some evidence of the existence of a cutoff time scale below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. (2011) using quasar light curves from Kepler. On very long time scales (> a few years), the light curves do not constrain models well, but are generally consistent with the DRW model.

View original: http://arxiv.org/abs/1202.3783