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Artigo Multifractality signatures in quasars time series – I. 3C 273(Oxford University Press (OUP), 2018-05-18) Martins, Bruno Leonardo Canto; Belete, A. Bewketu; Bravo, J. P.; Leão, I. C.; Araujo, J. M. de; Medeiros, J.R. deThe presence of multifractality in a time series shows different correlations for different timescales as well as intermittent behaviour that cannot be captured by a single scaling exponent. The identification of a multifractal nature allows for a characterization of the dynamics and of the intermittency of the fluctuations in non-linear and complex systems. In this study, we search for a possible multifractal structure (multifractality signature) of the flux variability in the quasar 3C 273 time series for all electromagnetic wavebands at different observation points, and the origins for the observed multifractality. This study is intended to highlight how the scaling behaves across the different bands of the selected candidate, which can be used as an additional new technique to group quasars based on the fractal signature observed in their time series and determine whether quasars are non-linear physical systems or not. The multifractal detrended moving average algorithm (MFDMA) has been used to study the scaling in non-linear, complex, and dynamic systems. To achieve this goal, we applied the backward (θ = 0) MFDMA method for one-dimensional signals. We observe weak multifractal (close to monofractal) behaviour in some of the time series of our candidate except in the mm, UV and X-ray bands. The non-linear temporal correlation is the main source of the observed multifractality in the time series whereas the heaviness of the distribution contributes less.Artigo A Novel Approach to Study the Variability of NGC 5548(American Astronomical Society, 2019-07-12) Martins, Bruno Leonardo Canto; Belete, A. Bewketu; Goicoechea, L. J.; Leão, I.C.; Medeiros, J.R. deUnderstanding the properties of the continuum radiation and broad emission lines of active galactic nuclei provides significant information not only to model the radiation mechanism and constrain the geometry and kinematics ofthe broad-line region (BLR) but also to probe the central engine of the sources. Here we investigate the multifractal behavior of the Hβ emission line and the 5100 Å continuum flux light curves of NGC 5548. The aim is to search for multiscaling signatures in the light curves and check if there is a possible nonlinear relationship between them. To this end, we use a multifractality analysis technique called the Multifractal Detrended Moving Average analysis. We detect multifractal (nonlinear) signatures in the full monitoring and densely sampled period of the Hβ line and 5100 Å continuum light curves of NGC 5548, possibly indicating the presence of complex and nonlinear interaction in the 5100 Å continuum and Hβ emission line regions. Moreover, the degree of multifractality of the Hβ line is found to be about twice that of the 5100 Å continuum. The nonlinearity of both emissions could be generated when the BLR reprocesses the radiation from the central compact source. Finally, we found that antipersistent long-range temporal correlation is the main source of the multifractality detected in both light curves.