Related papers: Long Term Variability of SDSS Quasars

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…

Variability in the X-rays is a key ingredient in understanding and unveiling active galactic nuclei (AGN) properties. In this band flux variations occur on short time scales (hours) as well as on larger times scales. While short time scale…

We characterize the optical variability properties of eight lobe-dominated radio quasars (QSOs): B2 0709$+$37, FBQS J095206.3$+$235245, PG 1004$+$130, [HB89] 1156$+$631, [HB89] 1425$+$267, [HB89] 1503$+$691, [HB89] 1721$+$343, 4C $+$74.26,…

The variability of 30 PG quasars has been observed in the red band during three years. A rest-frame structure function analysis shows an increase of variability with the time interval up to 0.2 mag r.m.s. after two years. A comparison with…

The UV/optical variation, likely driven by accretion disc turbulence, is a defining characteristic of type 1 active galactic nuclei (AGNs) and quasars. In this work we investigate an interesting consequence of such turbulence using quasars…

The ubiquitous variability of quasars across a wide range of wavelengths and timescales encodes critical information about the structure and dynamics of the circumnuclear emitting regions that are too small to be directly resolved, as well…

We present a two-epoch Sloan Digital Sky Survey and Gemini/GMOS+William Herschel Telescope/ISIS variability study of 50 broad absorption line quasars of redshift range 1.9 < z < 4.2, containing 38 Si IV and 59 C IV BALs and spanning…

We investigated the optical/ultraviolet (UV) color variations for a sample of 2169 quasars based on multi-epoch spectroscopy in the Sloan Digital Sky Survey (SDSS) data release seven (DR7) and data release nine (DR9). To correct the…

Using the radio observations by FIRST and NVSS, we build a sample of 151 radio variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (probably another two) among them are classified as broad absorption…

We study the dependence of the number density and properties of quasars on the background galaxy density using the currently largest spectroscopic datasets of quasars and galaxies. We construct a galaxy number density field smoothed over…

When a flux-limited quasar sample is observed at later times, there will be more dimmed quasars than brightened ones, due to a selection bias induced at the time of sample selection. Quasars are continuously varying and there are more…

We characterize the optical variability of quasars in the intermediate Palomar Transient Factory (iPTF) and Palomar Transient Factory (PTF) surveys. We re-calibrate the $r$-band light curves for $\sim$28,000 luminous, broad-line AGNs from…

In this work we train three decision-tree based ensemble machine learning algorithms (Random Forest Classifier, Adaptive Boosting and Gradient Boosting Decision Tree respectively) to study quasar selection in the variable source catalog in…

Based on the Seventh Data Release (DR7) quasar catalog from the Sloan Digital Sky Survey, we investigate the variability of optical quasars in W1, W2, W3 and W4 bands of the Wide-field Infrared Survey Explorer (WISE) and the Near-Earth…

Based on a 20-year-long multiband observation of its light-curve, it was conjectured that the quasar SDSSJ025214.67-002813.7 has a periodicity of ~4.4 years. These observations were acquired at a highly irregular sampling rate and feature…

There is a large degree of variety in the optical variability of quasars and it is unclear whether this is all attributable to a single (set of) physical mechanism(s). We present the results of a systematic search for major flares in AGN in…

We present a multi-epoch study of the extreme X-ray variability of the type~1 quasar SDSS~J000532.84+200717.4 using archival observations from \textit{XMM-Newton}, \textit{Swift}/XRT, \textit{EP-FXT}, and \textit{ROSAT}, together with new…

We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the…

We investigate the variability properties of main sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction, and find that 60% of stars are more variable then the active Sun. We define low…

We present the discovery of six new quasars at z~6 selected from the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator. The six quasars are about two…