Early Warning Signals Indicate a Critical Transition in Betelgeuse

TL;DR

This study investigates the 2019-20 Betelgeuse dimming event, providing evidence that it was a critical transition in the star's pulsation dynamics indicated by rising early warning signals in its light curve.

Contribution

The paper demonstrates that early warning signals can identify critical transitions in stellar pulsation dynamics, specifically applied to Betelgeuse's recent dimming event.

Findings

Significant increase in autocorrelation, variance, and DFA spectral coefficient prior to dimming

Evidence supports a nonlinear dynamical transition as the cause of dimming

Minimal change in temperature and infrared flux suggests pulsation dynamics as the trigger

Abstract

Critical transitions occur in complex dynamical systems, when the system dynamics undergoes a regime shift. These can often occur with little change in the mean amplitude of system response prior to the actual time of transition. The recent dimming and brightening event in Betelgeuse occured as a sudden shift in the brightness and has been the subject of much debate. Internal changes or an external dust cloud have been suggested as reasons for this change in variability. We examine whether the dimming and brightening event of 2019-20 could be due to a critical transition in the pulsation dynamics of Betelgeuse, by studying the characteristics of the light curve prior to transition. We calculate the quantifiers hypothesised to rise prior to a critical transition for the light curve of Betelgeuse upto the dimming event of 2019-20. These include the autocorrelation at lag-1, variance and the spectral coefficient calculated from detrended fluctation analysis (DFA), apart from two measures that quantify the recurrence properties of the light curve. Significant rises are confirmed using the Mann-Kendall trend test. We see a significant increase in all quantifiers (p < 0.05) prior to the dimming event of 2019-20. This suggests that the event was a critical transition related to the underlying nonlinear dynamics of the star. Together with results that suggests minimal change in $T_{eff}$ and infra-red flux, a critical transition in the pulsation dynamics could be a possible reason for the unprecedented dimming of Betelgeuse. The rise in the studied quantifiers prior to the dimming event, supports this possibility.