Episodic Gaseous Outflows and Mass Loss from Red Supergiants

Abstract

The red hypergiant VY CMa and the more typical red supergiant (RSG) Betelgeuse provide clear observational evidence for discrete, directed gaseous outflows in their optical and infrared imaging, spectra, and light curves. In the very luminous VY CMa, mass-loss estimates from the infrared-bright knots and clumps not only dominate its measured overall mass loss, but explain it. In the less luminous Betelgeuse, similar mass estimates of its circumstellar condensations show that they contribute significantly to its measured mass-loss rate. We present new measurements for both stars and discuss additional evidence for gaseous ejections in other RSGs. Gaseous outflows are the dominant mechanism for the most luminous RSGs and an important contributor to the more typical RSGs like Betelgeuse. We conclude that gaseous outflows, related to magnetic fields and surface activity, comparable to coronal mass ejections, are a major contributor to mass loss from RSGs and the missing component in discussions of their mass-loss mechanism.