Journal
ASTROPHYSICAL JOURNAL
Volume 758, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/758/2/104
Keywords
accretion, accretion disks; galaxies: active; galaxies: nuclei; quasars: general; techniques: photometric
Categories
Funding
- NSFC [11033001]
- 973 program in China [2007CB8154505]
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- American Museum of Natural History
- Astrophysical Institute Potsdam
- University of Basel
- University of Cambridge
- Case Western Reserve University
- University of Chicago
- Drexel University
- Fermilab
- Institute for Advanced Study
- Japan Participation Group
- Johns Hopkins University
- Joint Institute for Nuclear Astrophysics
- Kavli Institute for Particle Astrophysics and Cosmology
- Korean Scientist Group
- Chinese Academy of Sciences (LAMOST)
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max- Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- Ohio State University
- University of Pittsburgh
- University of Portsmouth
- Princeton University
- United States Naval Observatory
- University of Washington
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We investigate the optical variability of 7658 quasars from SDSS Stripe 82. Taking advantage of a larger sample and relatively more data points for each quasar, we estimate variability amplitudes and divide the sample into small bins of redshift, rest-frame wavelength, black hole mass, Eddington ratio, and bolometric luminosity, respectively, to investigate the relationships between variability and these parameters. An anti-correlation between variability and rest-frame wavelength is found. The variability amplitude of radio-quiet quasars shows almost no cosmological evolution, but that of radio-loud ones may weakly anti-correlate with redshift. In addition, variability increases as either luminosity or Eddington ratio decreases. However, the relationship between variability and black hole mass is uncertain; it is negative when the influence of Eddington ratio is excluded, but positive when the influence of luminosity is excluded. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. Assuming that quasar variability is caused by variations of accretion rate, the Shakura-Sunyaev disk model can reproduce the tendencies of observed correlations between variability and rest-frame wavelength, luminosity as well as Eddington ratio, supporting that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model.
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