The Unexpected Spectrum of the Innermost Ejecta of the Red Hypergiant VY CMa
Journal article, 2019
Hubble Space Telescope/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 hundreds of au from the star. The K I lines are 10-20 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.
stars: mass-loss
line: identification
ISM: molecules
stars: massive
circumstellar matter
stars: individual (VY Canis Majoris)
stars: winds, outflows
Author
Roberta M. Humphreys
University of Minnesota
L. M. Ziurys
University of Arizona
J. J. Bernal
University of Arizona
Michael S. Gordon
NASA Ames Research Center
L. Andrew Helton
NASA Ames Research Center
Kazunori Ishibashi
Nagoya University
Terry J. Jones
University of Minnesota
A. M. S. Richards
University of Manchester
Wouter Vlemmings
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 874 2 L26Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Theoretical Chemistry
Infrastructure
Onsala Space Observatory
DOI
10.3847/2041-8213/ab11e5