Fractal analysis in pulsating stars: what is and what we can learn from it

Fractal and multi-fractal properties have been found both in fluid mechanics and geophysical related geometrical objects, as the convective boundary layer of cumulus cloud fields, ripple-wave turbulence, topographic and river networks patterns, solar granulation patterns, and in observational astrophysical time series, like light curves and velocity curves from pulsating stars. The main interest in the study of (multi)fractal properties in such physical phenomena lies in the close relationships they have with different underlying dynamic, i.e. depending on the system, chaos, turbulence, stochastic reaction-diffusion processes.

In this talk I will introduce the concepts of fractal, multi-fractal and self affine objects, and a wide range of statistical tools for their analysis. Then I will describe the basic ideas of my line of research, concerning the develop of classification criteria and algorithms for the identification of delta Scuti, gamma Doradus and Solar-like pulsating stars, based on chaos analysis and multi-fractal analysis. In fact multi-fractal behaviour in light curves, which emerges at the onset of chaos, could be the fingerprint of the stochastic mechanism of modes excitation, due to an outer convective layer. In this framework of study it could be possible to link the fractal behaviours of time series with the heavy tailed distribution of the granulation dynamics, which is a good indication of self-affinity.

06/04/2017 - 12:30
Dr. Sebastiano de Franciscis