The Evolving Light Variations and Periodicities of Betelgeuse Five Years after the Great Dimming

Abstract Betelgeuse is the brightest red supergiant visible from Earth. Betelgeuse has nearly 200 yr of visual observations as well as systematic photoelectric and CCD data that indicate semi-regular light variations. In mid-February 2020, Betelgeuse surprisingly faded to its faintest and coolest ever recorded—dubbed the “Great Dimming” ( V +1.61 mag). Previously, Betelgeuse had multiple periodicities with dominant periods of 185, 380–420, and 2000–2200 days. We find that even before this dimming, a new dominant period of 208 ±12 days superseded the 400 days periodicity. Additionally present is a 2000–2200 days Long Secondary Period (LSP) that remains consistent throughout the dimming. The LSP has recently been proposed to arise from a close-orbiting binary companion star. Contrary to expectation, however, the LSP light minimum appears to be occurring several months earlier than predicted. We present results of quantitative period analyses and draw tentative conclusions.