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Optical variability of quasars: a damped random walk

Published online by Cambridge University Press:  25 July 2014

Željko Ivezić  and
Chelsea MacLeod
Željko Ivezić
Affiliation:
Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580, USA email: ivezic@astro.washington.edu
Chelsea MacLeod
Affiliation:
Department of Physics, U. S. Naval Academy, 572c Holloway Rd, Annapolis, MD 21402, USA email: macleod@usna.edu
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Abstract

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A damped random walk is a stochastic process, defined by an exponential covariance matrix that behaves as a random walk for short time scales and asymptotically achieves a finite variability amplitude at long time scales. Over the last few years, it has been demonstrated, mostly but not exclusively using SDSS data, that a damped random walk model provides a satisfactory statistical description of observed quasar variability in the optical wavelength range, for rest-frame timescales from 5 days to 2000 days. The best-fit characteristic timescale and asymptotic variability amplitude scale with the luminosity, black hole mass, and rest wavelength, and appear independent of redshift. In addition to providing insights into the physics of quasar variability, the best-fit model parameters can be used to efficiently separate quasars from stars in imaging surveys with adequate long-term multi-epoch data, such as expected from LSST.

Keywords

surveysgalaxies: activequasars: generalstars: variablesstars: statistics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S304: Multiwavelength AGN Surveys and Studies , October 2013 , pp. 395 - 398
Copyright
Copyright © International Astronomical Union 2014 

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