The unique dynamical system underlying RR Lyrae pulsations

TL;DR

This paper explores the complex nonlinear dynamics of RR Lyrae star pulsations, emphasizing the importance of high order resonances and chaotic attractors, which may shed light on the Blazhko effect.

Contribution

It reveals the crucial role of high order resonances and chaos in RR Lyrae pulsations, challenging simpler models and highlighting the need to consider mode interactions.

Findings

High order resonances significantly influence RR Lyrae pulsations.

Chaotic attractors are present at multiple time scales.

Mode interactions are key to understanding the Blazhko effect.

Abstract

Hydrodynamic models of RR Lyrae pulsation display a very rich behaviour. Contrary to earlier expectations, high order resonances play a crucial role in the nonlinear dynamics representing the interacting modes. Chaotic attractors can be found at different time scales: both in the pulsation itself and in the amplitude equations shaping the possible modulation of the oscillations. Although there is no one-to-one connection between the nonlinear features found in the numerical models and the observed behaviour, the richness of the found phenomena suggests that the interaction of modes should be taken seriously in the study of the still unsolved puzzle of Blazhko effect. One of the main lessons of this complex system is that we should rethink the simple interpretation of the observed effect of resonances.