The solar activity by wavelet-based multifractal analysis

Maruyama, Fumio

doi:10.1016/j.nrjag.2016.10.003

Cited by 2 publications

(5 citation statements)

References 6 publications

(7 reference statements)

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“…Because of its capability of decomposing a signal into small fractions that are well localized in time and frequency and detecting local irregularities of a signal (areas of the signal where a particular derivative is not continuous) such as nonstationarity, oscillatory behaviour, breakdown, discontinuity in higher derivatives, the presence of long-range dependence, and other trends (Maruyama 2016b;Puckovs & Matvejevs 2012), wavelet analysis remains one of the most preferred signal analysis techniques to date. Additionally, there is a claim that wavelet transforms are suitable for multifractal analysis and allow reliable multifractal analysis to be performed (Muzy et al 1991).…”

Section: Methods and Proceduresmentioning

confidence: 99%

“…In addition, Belete et al (2018a) verified that redshift correction does not affect quasars' multifractality behaviour, which is the same in both the observed and rest frames of quasars. Multifractality analysis has been applied in different science cases (e.g., Maruyama et al 2017;Maruyama 2016a;Kasde et al 2016;Agarwal et al 2016;de Freitas et al 2016;Aliouane & Ouadfeul 2013;Jagtap et al 2012;Ouahabi & Femmam 2011;Nurujjaman et al 2009;Lin & Sharif 2007;Degaudenzi & Arizmendi 1998). Our work is organized as follows.…”

Section: Introductionmentioning

confidence: 99%

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Revealing the non-linear behaviour of the lensed quasar Q0957+561

Belete

Martins

Leão

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Knowledge about how the nonlinear behaviour of the intrinsic signal from lensed background sources changes on its path to the observer provides much information, particularly about the matter distribution in lensing galaxies and the physical properties of the current universe, in general. Here, we analyse the multifractal (nonlinear) behaviour of the optical observations of A and B images of Q0957+561 in the r and g bands. AIMS: To verify the presence, or absence, of extrinsic variations in the observed signals of the quasar images and investigate whether extrinsic variations affect the multifractal behaviour of their intrinsic signals. METHOD: We apply a wavelet transform modulus maxima-based multifractality analysis approach. RESULTS: We detect strong multifractal (nonlinear) signatures in the light curves of the quasar images. The degree of multifractality for both images in the r band changes over time in a non-monotonic way, possibly indicating the presence of extrinsic variabilities in the light curves of the images, i.e., the signals of the quasar images are a combination of both intrinsic and extrinsic signals. Additionally, in the r band, in periods of quiescent microlensing activity, we find that the degree of multifractality (nonlinearity) of image A is stronger than that of B, while B has a larger multifractal strength in recent epochs (from day 5564 to day 7527) when it appears to be affected by microlensing. Finally, comparing the optical bands in a period of quiescent microlensing activity, we find that the degree of multifractality is stronger in the r band for both quasar images. In the absence of microlensing, the observed excesses of nonlinearity are most likely generated when the broad-line region (BLR) reprocesses the radiation from the compact sources.

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Section: Methods and Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Revealing the non-linear behaviour of the lensed quasar Q0957+561

Belete

Martins

Leão

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…The continuous wavelet transform is an excellent tool for mapping the changing properties of nonstationary signals. Because of its capability of decomposing a signal into small fractions that are well localized in time and frequency and of detecting local regularities of a signal (areas on the signal where a particular derivative is not continuous) such as nonstationarity, oscillatory behavior, breakdown, discontinuity in higher derivatives, the presence of long-range dependence, and other trends, wavelet analysis remains one of the most preferable signal analysis techniques to date (Maruyama 2016 ;Andrejs Puckovs & Andrejs Matvejevs 2012 ). These strengths of wavelet transform make it preferable to other traditional singularity analysis techniques, and there is a claim that it is suitable for multifractal analysis and allows for reliable multifractal analysis to be performed Muzy & Arneodo (1991 ).…”

Section: Methods and Proceduresmentioning

confidence: 99%

“…Most astrophysical objects are possibly associated with continuous nonlinear stochastic systems due to their complexity in nature. A fractal behavior can be observed in the time series of complex systems (Maruyama 2016 ). It has been shown that quasars, in general, are among complex systems that have nonlinear time series characterized by fractal behavior ( Vio 1991 ) and also by sudden bursts of very large amplitude (Barbieri 1990 ;Kidger 1989 ), which implies that the dynamical evolution of quasars is nonlinear (i.e., described by nonlinear stochastic differential equations) ( Vio 1991 ).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, Bewketu Belete et al (2018 ) has studied the fractal nature of the light curves of 3C 273 at specific frequencies across its electromagnetic spectrum and shown that most of the light curves have presented a multifractal signature, confirming the nonlinear and intermittent nature of the source. For more studies on multifractality analysis by different authors in different science cases, see Maruyama (2017Maruyama ( , 2016; Kasde (2016 ); Agarwal (2016 ); de Freitas (2016 ); Aliouane & Ouadfeul (2013); Jagtap (2012 ); Ouahabi & Femmam (2011 ); Nurujjaman (2009 ); Lin & Sharif (2007 ); Degaudenzi & Arizmendi (1998 ). The aims of our work are as follows: (i) to study the multifractal behavior (if any) of selected radio-loud quasars located at different redshifts, (ii) to verify how fractal signatures of each source, and between sources, behave at 22 and 37 GHz (any similarity or difference?…”

Section: Introductionmentioning

confidence: 99%

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Cosmological Evolution of Quasar Radio Emission in the View of Multifractality

Belete

Femmam

Tornikosk

et al. 2019

ApJ

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Variations in scaling behavior in the flux and emissions of distant astronomical sources with respect to their cosmic time are important l phenomena that can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Different studies have been applying linear analysis to understand and model quasars' light curves. Here, we study the multifractal behavior of selected quasars' radio emissions in their observed frame (at 22 and 37 GHz bands) and and their rest frame. To this end, we apply the wavelet transform-based multifractal analysis formalism called wavelet transform modulus maxima. In addition, we verify whether the autoregressive integrated moving average (ARIMA) models fit our data or not. In our work, we observe strong multifractal behavior for all the sources. Additionally, we find that the degree of multifractality is strongly similar for each source and significantly different between sources at 22 and 37 GHz. This similarity implies that the two frequencies have the same radiation region and mechanism, whereas the difference indicates that the sources have intrinsically different dynamics. Furthermore, we show that the degree of multifractality is the same in the observed and rest frames of the quasars, i.e., multifractality is an intrinsic property of radio quasars. Finally, we show that the ARIMA models fit the 3C 345 quasar at 22 GHz and partially fit most of the time series with the exception of the 3C 273 and 3C 279 quasars at 37 GHz, for which the models are found to be inadequate.

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The solar activity by wavelet-based multifractal analysis

Cited by 2 publications

References 6 publications

Revealing the non-linear behaviour of the lensed quasar Q0957+561

Revealing the non-linear behaviour of the lensed quasar Q0957+561

Cosmological Evolution of Quasar Radio Emission in the View of Multifractality

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