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We present the characterization and initial results from the QUEST–La Silla active galactic nucleus AGNvariability survey. This is an effort to obtain well-sampled optical light curves in extragalactic fields with uniquemultiwavelength observations. We present photometry obtained from 2010 to 2012 in the XMM-COSMOS field,which was observed over 150 nights using the QUEST camera on the European Southern ObservatoryESO Schmidt telescope. The survey uses a broadband filter, the Q band, similar to the union of the g and the rfilters, achieving an intrinsic photometric dispersion of 0.05 mag and a systematic error of 0.05 mag in thezero point. Since some detectors of the camera show significant nonlinearity, we use a linear correlation to fit thezero points as a function of the instrumental magnitudes, thus obtaining a good correction to the nonlinear behaviorof these detectors. We obtain good photometry to an equivalent limiting magnitude of r ~ 20.5. The astrometryhas an internal precision of ~ 0. 1 and an overall accuracy of 0. 2 when compared to the Sloan Digital Sky Survey.Studying the optical variability of X-ray-detected sources in the XMM-COSMOS field, we find that the survey is∼75%–80% complete to magnitudes r ~ 20, and ∼67% complete to a magnitude r ~ 21. Additionally, broad-lineBL AGNs have larger variation amplitude than non-broad-line NL AGNs, with ∼80% of the BL AGNsclassified as variable, while only ∼21% of the NL AGNs are classified as variable. We also find that ∼22% ofobjects classified as galaxies GALs are also variable. The determination and parameterization of the structurefunction SFnorm t t = A g of the variable sources show that most BL AGNs are characterized by A > 0.1 andg > 0.025. It is further shown that NL AGNs and GAL sources occupying the same parameter space in A and γ arevery likely to correspond to obscured or low-luminosity AGNs. Our samples are, however, small, and we expect torevisit these results using larger samples with longer light curves obtained as part of our ongoing surveyNota general

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Author: Cartier Ugarte, Regis; - Lira Teillery, Paulina; - Coppi, Paolo; - Sánchez, Paula; - Arévalo, Patricia; - Bauer, Franz; - Rabin

Source: http://repositorio.uchile.cl/



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