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Paper: Long-Term Optical Quasar Variability
Volume: 360, AGN Variability from X-Rays to Radio Waves
Page: 29
Authors: de Vries, W.H.; Becker, R.H.; White, R.L.
Abstract: We have used a large sample of 41,391 spectroscopically confirmed quasars, taken from the Sloan Digital Sky Survey Data Release 2 (DR2) and from the 2dF QSO Redshift Survey, to investigate the long term optical variability of quasars. The recent DR2 photometric information for the quasars can be combined with re-calibrated archival survey data to extend the variability time baseline towards ~ 50 years. Based on structure function analysis, we conclude that quasar variability is intrinsic to the AGNs, and is caused by chromatic outbursts / flares with a limited luminosity range and varying time-scales, which have an asymmetric overall light-curve shape. Currently the model that has the most promise of fitting the observations is based on accretion-disk instabilities.
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