Quasar Variability from Microlensing

1996 ◽  
pp. 291-292
Author(s):  
M. R. S. Hawkins
Keyword(s):  
Quasar Variability

Quasar Variability and Gravitational Microlensing

1997 ◽  
Vol 482 (1) ◽  
pp. L5-L8 ◽  
Author(s):  
M. R. S. Hawkins ◽  
A. N. Taylor
Keyword(s):  
Gravitational Microlensing ◽  
Quasar Variability

scholarly journals QUANTIFYING QUASAR VARIABILITY AS PART OF A GENERAL APPROACH TO CLASSIFYING CONTINUOUSLY VARYING SOURCES

2009 ◽  
Vol 708 (2) ◽  
pp. 927-945 ◽  
Author(s):  
Szymon Kozłowski ◽  
Christopher S. Kochanek ◽  
A. Udalski ◽  
Ł. Wyrzykowski ◽  
I. Soszyński ◽  
...  
Keyword(s):  
Quasar Variability

scholarly journals The correlations between optical variability and physical parameters of quasars in SDSS Stripe 82

2012 ◽  
Vol 8 (S290) ◽  
pp. 373-374
Author(s):  
Wenwen Zuo ◽  
Xue-Bing Wu ◽  
Yi-Qing Liu ◽  
Cheng-Liang Jiao
Keyword(s):  
Black Hole ◽  
Rest Frame ◽  
Accretion Rate ◽  
Physical Parameters ◽  
Optical Variability ◽  
Black Hole Mass ◽  
Disk Model ◽  
Bolometric Luminosity ◽  
Data Points ◽  
Quasar Variability

AbstractWe 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.

scholarly journals Intrinsic quasar variability and time delay determination in the lensed quasar UM673

2010 ◽  
Vol 401 (4) ◽  
pp. 2805-2815 ◽  
Author(s):  
E. Koptelova ◽  
V. L. Oknyanskij ◽  
B. P. Artamonov ◽  
O. Burkhonov
Keyword(s):  
Time Delay ◽  
Quasar Variability

scholarly journals Gaiareference frame amid quasar variability and proper motion patterns in the data

2016 ◽  
Vol 589 ◽  
pp. A71 ◽  
Author(s):  
R. K. Bachchan ◽  
D. Hobbs ◽  
L. Lindegren
Keyword(s):  
Proper Motion ◽  
Motion Patterns ◽  
Quasar Variability

scholarly journals A Sample Bias in Quasar Variability Studies

2021 ◽  
Vol 918 (1) ◽  
pp. L19
Author(s):  
Yue Shen ◽  
Colin J. Burke
Keyword(s):  
Sample Bias ◽  
Quasar Variability

scholarly journals Correlation between optical and UV variability of a large sample of quasars

2020 ◽  
Vol 495 (1) ◽  
pp. 1403-1413
Author(s):  
Chengcheng Xin ◽  
Maria Charisi ◽  
Zoltán Haiman ◽  
David Schiminovich
Keyword(s):  
Galaxy Evolution ◽  
Light Curves ◽  
Small Samples ◽  
Strongly Correlated ◽  
Large Sample ◽  
Physical Conditions ◽  
Accretion Rates ◽  
The Galaxy ◽  
Multiple Wavelengths ◽  
Quasar Variability

ABSTRACT The variability of quasars across multiple wavelengths is a useful probe of physical conditions in active galactic nuclei. In particular, variable accretion rates, instabilities, and reverberation effects in the accretion disc of a supermassive black hole are expected to produce correlated flux variations in ultraviolet (UV) and optical bands. Recent work has further argued that binary quasars should exhibit strongly correlated UV and optical periodicities. Strong UV–optical correlations have indeed been established in small samples of (N ≲ 30) quasars with well-sampled light curves, and have extended the ‘bluer-when-brighter’ trend previously found within the optical bands. Here, we further test the nature of quasar variability by examining the observed-frame UV–optical correlations among bright quasars extracted from the Half Million Quasars (HMQ) catalogue. We identified a large sample of 1315 quasars in HMQ with overlapping UV and optical light curves from the Galaxy Evolution Explorer and the Catalina Real-time Transient Survey, respectively. We find that strong correlations exist in this much larger sample, but we rule out, at ∼95 per cent confidence, the simple hypothesis that the intrinsic UV and optical variations of all quasars are fully correlated. Our results therefore imply the existence of physical mechanism(s) that can generate uncorrelated optical and UV flux variations.

ERRATUM: “A DESCRIPTION OF QUASAR VARIABILITY MEASURED USING REPEATED SDSS AND POSS IMAGING” (2012, ApJ, 753, 106)

2014 ◽  
Vol 782 (2) ◽  
pp. 119 ◽  
Author(s):  
Chelsea L. MacLeod ◽  
Željko Ivezić ◽  
Branimir Sesar ◽  
Wim de Vries ◽  
Christopher S. Kochanek ◽  
...  
Keyword(s):  
Quasar Variability

scholarly journals Testing the Standard Model of Active Galactic Nuclei through Quasar Variability

2011 ◽  
Vol 7 (S285) ◽  
pp. 312-314
Author(s):  
Alessandro Ederoclite ◽  
Jana Polednikova ◽  
Jordi Cepa ◽  
José Antonio de Diego Onsurbe ◽  
Ignacio González-Serrano
Keyword(s):  
Standard Model ◽  
Active Galactic Nuclei ◽  
Central Region ◽  
Galactic Nuclei ◽  
Temporal Variations ◽  
The Standard Model ◽  
Multi Wavelength ◽  
Quasar Variability

AbstractThe standard model of Active Galactic Nuclei (AGNs) predicts that Type 2 AGNs and Type 1 AGNs only differ in the orientation of a dust torus, which does or does not allow one to observe the central region. If the model is correct, the time-scales and the amplitudes of observed temporal variations should be different between obscured and unobscured objects. In order to test this hypothesis, we started a multi-wavelength (BRIJKs) monitoring campaign of a sample of quasars of both types. Here we present the data and preliminary results of that project.

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