The Unexpected Spectrum of the Innermost Ejecta of the Red Hypergiant VY CMa

Abstract

HST/STIS spectra of the small clumps and filaments closest to the central star in VY CMa reveal that the very strong K I emission and TiO and VO molecular emission, long thought to form in a dusty circumstellar shell, actually originate in a few small clumps 100's of AU from the star. The K I lines are 10 to 20 times stronger in these nearest ejecta than on the star. The observations also confirm VO as a circumstellar molecule. In this letter we discuss the spectra of the features, their motions and ages, and the identification of the molecular emission. The strength of the atomic and molecular features in the small clumps present an astrophysical problem for the excitation process. We show that the clumps must have a nearly clear line of sight to the star's radiation.

arXiv commentTo appear in the Astrophysical Journal

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• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
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• The Mass-Loss History of the Red Hypergiant VY CMa
• Red Supergiants, Yellow Hypergiants, and Post-RSG Evolution
• History of two mass loss processes in VY CMa. Fast outflows carving older ejecta
• Betelgeuse, the Prototypical Red Supergiant
• Molecules and Chemistry in Red Supergiants