The Correlations Between Optical Variability and Physical Parameters of Quasars in SDSS Stripe 82

Zuo, Wenping; Wu, Xue-Bing; Yi-qing, Liu; Jiao, Cheng-Liang

doi:10.1088/0004-637x/758/2/104

Cited by 95 publications

(174 citation statements)

References 42 publications

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“…This choice of rest-frame wavelength corresponds to what is observed within (i)PTF for z ∼ 1 quasars -typical of our sample. We note that our prescription is consistent with other estimates of the wavelength dependence of quasar variability from the same dataset (MacLeod et al 2010, Meusinger et al 2011, Zuo et al 2012). …”

Section: Wavelength Correctionsupporting

confidence: 90%

“…The relationship with black hole mass remains unclear, with different studies finding either positive, negative or absent correlations (Wold et al 2007, Wilhite et al 2008, Kelly et al 2009, MacLeod et al 2010, Zuo et al 2012). In the vast majority of cases (Andrae et al 2013), the variability is found to be of stochastic nature, with only a few recent claims of periodicity in a small number of objects (Graham et al 2015a, Graham et al 2015b, Charisi et al 2016, but see also Vaughan et al 2016).…”

Section: Nevencaplar@physethzch 1 Zwicky Fellowmentioning

confidence: 99%

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OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Čaplar

Lilly

Trakhtenbrot

2017

ApJ

116

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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 ∼28,000 luminous, broad-line AGNs from the SDSS, producing a total of ∼2.4 million photometric data points. We utilize both the structure function (SF) and power spectrum density (PSD) formalisms to search for links between the optical variability and the physical parameters of the accreting supermassive black holes that power the quasars. The excess variance (SF 2 ) of the quasar sample tends to zero at very short time separations, validating our re-calibration of the time-series data. We find that the the amplitude of variability at a given time-interval, or equivalently the time-scale of variability to reach a certain amplitude, is most strongly correlated with luminosity with weak or no dependence on black hole mass and redshift. For a variability level of SF(τ )=0.07 mag, the time-scale has a dependency of τ ∝ L 0.4 . This is broadly consistent with the expectation from a simple Keplerian accretion disk model, which provides τ ∝ L 0.5 . The PSD analysis also reveals that many quasar light curves are steeper than a damped random walk. We find a correlation between the steepness of the PSD slopes, specifically the fraction of slopes steeper than 2.5, and black hole mass, although we cannot exclude the possibility that luminosity or Eddington ratio are the drivers of this effect. This effect is also seen in the SF analysis of the (i)PTF data, and in a PSD analysis of quasars in the SDSS Stripe 82.

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Section: Wavelength Correctionsupporting

confidence: 90%

Section: Nevencaplar@physethzch 1 Zwicky Fellowmentioning

confidence: 99%

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Čaplar

Lilly

Trakhtenbrot

2017

ApJ

116

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“…These follow the anticorrelation with luminosity as has been found in several previous studies (e.g. Cristiani et al 1990;Vanden Berk et al 2004;Zuo et al 2012). …”

Section: Agn Variabilitysupporting

confidence: 89%

Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Greiner

Richter

2015

A&A

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Context. The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. Aims. We investigate two ROSAT All-Sky Survey fields of size 10 • × 10 • each, one at galactic latitude b = 83 • (26 Com), the other at b = −5 • (γ Sge), in order to optically identify the majority of sources. Methods. We used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All-Sky Survey sources. All objects fainter than about 12 mag and brighter than about 17 mag, in or near the error circle of the ROSAT positions, were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol.Results. The present paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analysed. In particular, we found 126 active galactic nuclei (some of them may be misclassified cataclysmic variables, CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13 mag, 7 UV Cet stars, 3 semiregular resp. slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant and 1 planetary nebula. As expected, nearly all active galactic nuclei are found in the high-galactic latitude field, while the majority of CVs is located at low galactic latitudes. We identify in total 72 new variable objects. Conclusions. X-ray emission is, expectedly, tightly correlated with optical variability, and thus our new method for optically identifying X-ray sources is demonstrated to be feasible. Given the large number of optical plates used, this method was most likely not more efficient than e.g. optical spectroscopy. However, it required no telescope time, only access to archival data.

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“…Wilhite et al 2005;Pu et al 2006;Meusinger et al 2011;Zuo et al 2012;Bian et al 2012a). The trend of bluer spectra during brighter phases is usually explained by the accretion variation.…”

Section: Introductionmentioning

confidence: 99%

Variability of QSOs with variable regions in broad absorption troughs from the Sloan Digital Sky Survey

He¹,

Bian²,

Ge³

et al. 2015

Mon. Not. R. Astron. Soc.

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The variability of broad absorption lines is investigated for a sample of 188 broad-absorptionline (BAL) quasars (QSOs) (z > 1.7) with at least two-epoch observations from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), covering a time-scale of about 0.001 -3 years in the rest frame. Considering only the longest time-scale between epochs for each QSO, 73 variable regions in the C IV BAL troughs are detected for 43 BAL QSOs. The proportion of BAL QSOs showing variable regions increases with longer time-interval than about 1 year in the rest frame. The velocity width of variable regions is narrow compared to the BALtrough outflow velocity. For 43 BAL QSOs with variable regions, it is found that there is a medium strong correlation between the variation of the continuum luminosity at 1500 Å and the variation of the spectral index. With respect to the total 188 QSOs, larger proportion of BAL QSOs with variable regions appears bluer during their brighter phases, which implies that the origin of BAL variable regions is related to the central accretion process. For 43 BAL QSOs with variable regions, it is possible that there is a negative medium strong correlation between the absolute variation of the equivalent width and the Mg II -based black hole mass, and a medium strong correlation between the maximum outflow velocity of variable regions and the Eddington ratio. These results imply the connection between the BAL-trough variation and the central accretion process.

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The Correlations Between Optical Variability and Physical Parameters of Quasars in SDSS Stripe 82

Cited by 95 publications

References 42 publications

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes

Variability of QSOs with variable regions in broad absorption troughs from the Sloan Digital Sky Survey

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