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We analyze the properties of quasar variability using repeated SDSS imaging data in five UV-to-far red photometric bands, accurate to 0.02 mag, for 13,000 spectroscopically confirmed quasars. The observed time lags span the range from 3…

We conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. We use a Bayesian quasar selection algorithm (Richards et al.…

We provide a quantitative description and statistical interpretation of the optical continuum variability of quasars. The Sloan Digital Sky Survey (SDSS) has obtained repeated imaging in five UV-to-IR photometric bands for 33,881…

We present a new and simple technique for selecting extensive, complete and pure quasar samples, based on their intrinsic variability. We parametrize the single-band variability by a power-law model for the light-curve structure function,…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Kasper B. Schmidt , Philip J. Marshall , Hans-Walter Rix , Sebastian Jester , Joseph F. Hennawi , Gregory Dobler

Using a sample of over 25000 spectroscopically confirmed quasars from the Sloan Digital Sky Survey, we show how quasar variability in the rest frame optical/UV regime depends upon rest frame time lag, luminosity, rest wavelength, redshift,…

Sloan Digital Sky Survey (SDSS) repeat spectroscopic observations have resulted in multiple-epoch spectroscopy for roughly 2500 quasars observed more than 50 days apart. From this sample, we identify 315 quasars that have varied…

We use a sample of 3791 quasars from the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR), and compare their photometry to historic plate material for the same set of quasars in order to study their variability properties. The time…

Astrophysics · Physics 2009-11-07 Wim de Vries , Bob Becker , Rick White

We develop a method for separating quasars from other variable point sources using SDSS Stripe 82 light curve data for ~10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by…

Cosmology and Nongalactic Astrophysics · Physics 2011-01-28 C. L. MacLeod , K. Brooks , Z. Ivezic , C. S. Kochanek , R. Gibson , A. Meisner , S. Kozlowski , B. Sesar , A. C. Becker , W. de Vries

The ensemble variability properties of nearly 23,000 quasars are studied using the Palomar-QUEST Survey. The survey has covered 15,000 square degrees multiple times over 3.5 years using 7 optical filters, and has been calibrated…

Cosmology and Nongalactic Astrophysics · Physics 2011-02-11 Anne Bauer , Charles Baltay , Paolo Coppi , Nancy Ellman , Jonathan Jerke , David Rabinowitz , Richard Scalzo

We present a new approach to analysing the dependence of quasar variability on rest-frame wavelengths. We exploited the spectral archive of the Sloan Digital Sky Survey (SDSS) to create a sample of more than 9000 quasars in the Stripe 82.…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 H. Meusinger , A. Hinze , A. de Hoon

Significant progress in the description of quasar variability has been recently made by employing SDSS and POSS data. Common to most studies is a fundamental assumption that photometric observations at two epochs for a large number of…

Astrophysics · Physics 2009-11-13 C. MacLeod , Z. Ivezic , W. de Vries , B. Sesar , A. Becker

Context: Quasar variability has proven to be a powerful tool to constrain the properties of their inner engine and the accretion process onto supermassive black holes. Correlations between UV/optical variability and physical properties have…

Astrophysics of Galaxies · Physics 2024-06-26 Vincenzo Petrecca , Iossif Papadakis , Maurizio Paolillo , Demetra De Cicco , Franz Bauer

By observing the high galactic latitude equatorial sky in drift scan mode with the QUEST (QUasar Equatorial Survey Team) Phase 1 camera, multi-bandpass photometry on a large strip of sky, resolved over a large range of time scales (from…

We present the ensemble variability analysis results of quasars using the Dark Energy Camera Legacy Survey (DECaLS) and the Sloan Digital Sky Survey (SDSS) quasar catalogs. Our dataset includes 119,305 quasars with redshifts up to 4.89.…

Astrophysics of Galaxies · Physics 2018-07-11 Zefeng Li , Ian D. McGreer , Xue-Bing Wu , Xiaohui Fan , Qian Yang

We present results from a monitoring program of 42 quasars from the Palomar Green sample. The objects were observed for 7 years at the Wise Observatory, as part of a long term effort to monitor AGN of various types. This is the most…

Astrophysics · Physics 2014-10-13 Uriel Giveon , Dan Maoz , Shai Kaspi , Hagai Netzer , Paul S. Smith

Quasars are variable and their variability can both constrain their physical properties and help to identify them. We look for ways to efficiently identify quasars exhibiting consistent variability over multi-year time-scales, based on a…

Astrophysics of Galaxies · Physics 2025-07-02 E. A. Zaharieva , V. D. Ivanov , E. P. Ovcharov , O. I. Stanchev

Variability is a striking features of quasars, observed at all timescales wavelengths. Studying its properties and the correlations with the physical parameters (e.g. black hole mass and accretion rate) provides significant insights into…

We present an improved photometric error analysis for the 7,100 CRTS (Catalina Real-Time Transient Survey) optical light curves for quasars from the SDSS (Sloan Digital Sky Survey) Stripe 82 catalogue. The SDSS imaging survey has provided a…

Astrophysics of Galaxies · Physics 2017-12-07 Krzysztof Suberlak , Željko Ivezić , Chelsea L. MacLeod , Matthew Graham , Branimir Sesar

The potential of the Sloan Digital Sky Survey for wide-field variability studies is illustrated using multi-epoch observations for 3,000,000 point sources observed in 700 deg2 of sky, with time spans ranging from 3 hours to 3 years. These…

We model the time variability of ~9,000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk. Using 2.7 million photometric measurements collected over 10 years, we confirm the results of Kelly et al. (2009) and…

Cosmology and Nongalactic Astrophysics · Physics 2010-09-07 C. L. MacLeod , Ž. Ivezić , C. S. Kochanek , S. Kozłowski , B. C. Kelly , E. Bullock , A. Kimball , B. Sesar , D. Westman , K. Brooks , R. Gibson , A. C. Becker , W. H. de Vries
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