Related papers: The Optical Variability of QSO's

The long-term variability of a sample of 149 optically selected QSOs in the field of the Selected Area 94 has been studied in the R-band. The relations between variability and luminosity and between variability and redshift have been…

The relationship between variability, luminosity and redshift in the South Galactic Pole QSO sample is examined in an effort to disentangle the effects of luminosity and redshift in the amplitude of the optical variations. The…

The relation between quasar variability and parameters such as luminosity and redshift has been a matter of hot debate over the last few years with many papers on the subject. Any correlations which can be established will have a profound…

A recently discovered inverse correlation between QSO redshift and long-term continuum variability timescales was suggested to be the signature of microlensing on cosmological scales (Hawkins 1993). A general theoretical method for…

The consistency of the Starburst model for AGN is tested using the optical variability observed in large data bases of QSOs. Theoretical predictions for the variability--luminosity relationship and structure function are presented and…

We present an analysis of X-ray variability in a sample of 156 radio quiet quasars taken from the ROSAT archive, covering a redshift range 0.1 < z < 4.1. A maximum likelihood method is used to constrain the amplitude of variability in these…

In this Paper we present a clustering analysis of QSOs as a function of luminosity over the redshift range z=0.3-2.9. We use a sample of 10566 QSOs taken from the preliminary data release catalogue of the 2dF QSO Redshift Survey (2QZ). We…

A new analysis of the variability of the spectral slope of PG QSOs has been performed, on the basis of recent literature data in the B and R photometric bands. Preliminary results confirm our previous findings concerning the increase of…

We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratorio Nacional de Astrofisica, Brazil, between March 1993 and July 1996. A distinctive feature of this…

We present a combined analysis of the optical spectral variability for two samples of QSOs, 42 objects at $z<0.4$ monitored at the Wise Observatory (Giveon et al 1999), plus 59 objects up to $z\sim 3$ in the field of the Magellanic Clouds,…

We present the first results from a pilot programme to monitor the short term optical variability in Broad Absorption Line system QSOs. Intra-night optical variations of ~5% were detected on time scales of ~ one hour in QSOs 0846+156 and…

We performed a new analysis of B and R light curves of a sample of PG quasars. We confirm the variability-redshift correlation and its explanation in terms of spectral variability, coupled with the increase of rest-frame observing frequency…

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,…

This paper presents results of a search for short-term variability in the optical band of selected high-luminosity, high-redshift radio-quiet quasars. Each quasar has been monitored typically for 2 - 4 hours with a time resolution of 2 - 5…

We present an analysis of X-ray variability in a flux limited sample of QSOs. Selected from our deep ROSAT survey, these QSOs span a wide range in redshift ($0.1<z<3.2$) and are typically very faint, so we have developed a method to…

We have analysed the optical luminosity-redshift distribution properties of bright QSOs, using a new large sample from the Hamburg/ESO survey. The sample provides insight into the hitherto poorly sampled bright tail of the luminosity…

A refined sample of 64 variable objects with stellar image structure has been identified in SA 57 to $B \sim 22.5$, over a time baseline of 15 years, sampled at 11 distinct epochs. The photometric data typically have a root-mean-square…

Using 7.5-year spectroscopic monitoring data of a sample of 17 Palomar-Green QSOs (PG QSOs) (z=0.061-0.371), we obtain the optical spectral slope for each object at all epochs by a power-law fit to the spectra in continuum bands. All of…

Several recent studies show that bright, intermediate and high redshift optically and radio selected QSOs are positively correlated with nearby galaxies on a range of angular scales up to a degree. Obscuration by unevenly distributed…

We have obtained single-epoch optical photometry for 201 quasars, taken from the FIRST Bright Quasar Survey, which span a wide range in radio loudness. Comparison with the magnitudes of these objects on the POSS-I plates provides by far the…