Multifractality Signatures in Lensed Quasars

TL;DR

This study investigates the multifractal properties of light curves from 14 gravitationally lensed quasars using wavelet analysis, revealing strong multifractality and potential links to quasar and lensing parameters, with implications for understanding quasar dynamics.

Contribution

It applies wavelet transform multifractal analysis to a new sample of lensed quasars and explores correlations with physical parameters, advancing the understanding of quasar variability.

Findings

Strong multifractal signatures in all analyzed light curves.

Degree of multifractality tends to decrease with larger quasar source size.

Potential correlation between multifractality and characteristic timescales.

Abstract

Variations in scaling behavior in the flux and emissions of gravitational lensed quasars can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Here, we study the multifractal behavior of the light curves of 14 lensed quasars with multiple images in the $r$ band, with redshift ranging from 0.657 to 2.730, in the search for potential differences in nonlinearity between the signals of the quasar multiple images. Among these lensed systems, nine present two images, two present three images, and three present four images. To this end, we apply the wavelet transform-based multifractal analysis formalism called Wavelet Transform Modulus Maxima (WTMM). We identify strong multifractal signatures in the light curves of the images of all analyzed lensed quasar systems, independently of the number of images, with a significant difference between the degree of multifractality of all the images and combinations. We have also searched for a possible connection between the degree of multifractality and the characteristic parameters related to the quasar source and the lensing galaxy. These parameters include the Einstein ring radius and the accretion disk size and the characteristic timescales related to microlensing variability. The analysis reveals some apparent trends, pointing to a decrease in the degree of multifractality with the increase of the quasar's source size and timescale. Using a larger sample and following a similar approach, the present study confirms a previous finding for the quasar Q0957+561.